Commanded JTAG test access port operations

ABSTRACT

The disclosure describes a novel method and apparatus for improving the operation of a TAP architecture in a device through the use of Command signal inputs to the TAP architecture. In response to a Command signal input, the TAP architecture can perform streamlined and uninterrupted Update, Capture and Shift operation cycles to a target circuit in the device or streamlined and uninterrupted capture and shift operation cycles to a target circuit in the device. The Command signals can be input to the TAP architecture via the devices dedicated TMS or TDI inputs or via a separate CMD input to the device.

CROSS REFERENCE TO RELATED PATENTS

This application is a divisional of prior application Ser. No.16/824,333, filed Mar. 19, 2020, currently pending;

Which was a divisional of prior application Ser. No. 16/009,731, filedJun. 15, 2018, now U.S. Pat. No. 10,634,719, granted Apr. 28, 2020;

Which was a divisional of prior application Ser. No. 15/152,127, filedMay 11, 2016, now U.S. Pat. No. 10,024,913, granted Jul. 17, 2018;

Which was a divisional of prior application Ser. No. 14/809,880, filedJul. 27, 2015, now U.S. Pat. No. 9,366,726, granted Jun. 14, 2016;

Which was a divisional of prior application Ser. No. 14/589,420, filedJan. 5, 2015, now U.S. Pat. No. 9,121,905, granted Sep. 1, 2015;

Which was a divisional of prior application Ser. No. 14/031,243, filedSep. 19, 2013, now U.S. Pat. No. 8,959,396, granted Feb. 17, 2015;

Which was a divisional of prior application Ser. No. 13/028,575, filedFeb. 16, 2011, now U.S. Pat. No. 8,572,433, granted Oct. 29, 2013;

And claims priority from Provisional Application No. 61/312,384, filedMar. 10, 2010.

The disclosure relates to some extent to application Ser. No.12/410,561, filed Mar. 25, 2009, which is incorporated herein byreference.

FIELD OF THE DISCLOSURE

This disclosure relates generally to the operation of JTAG test accessports (TAPs) in devices and in particular to a method of streamliningthe operation of TAPs using commands.

BACKGROUND OF THE DISCLOSURE

Most devices today, which may be integrated circuit (IC) devices orembedded core devices within an IC, include an IEEE standard 1149.1(JTAG) Test Access Port (TAP) architecture to access target circuitswithin the devices. The TAP includes an interface which comprises a testdata input (TDI) signal, a test clock (TCK) signal, a test mode select(TMS) signal, a test data output (TDO) signal and an optional test resetsignal. Devices also use other IEEE standards that are based on the IEEE1149.1 TAP such as but not limited to IEEE 1149.4, IEEE 1149.6, IEEE1149.7, IEEE P1149.8.1, IEEE 1532, and IEEE P1687. The TAP is used tocontrol various activities in the device such as but not limited too,device to device boundary scan testing, device testing, devicedebugging, and device programming.

FIG. 1 illustrates an example implementation of a TAP within a device102. The TAP includes a TAP state machine (TSM) 104, an instructionregister 106, two or more data registers 108, a data register control(DRC) router, multiplexers 112 and 114, a falling TCK edge operated TDOregister (R) 116, and TDO buffer 118. The TSM operates in response tothe TCK and TMS input signals to; (1) place the TAP is a Test LogicReset state, (2) place the TAP in a Run Test/Idle state, (3) perform ascan operation to the instruction register from TDI to TDO, or (4) toperform scan operation to a selected data register from TDI to TDO.

During instruction scan operations, the TSM outputs a bus of instructionregister control (IRC) signals to the instruction register, a select(SEL) signal to multiplexer 114, and an enable (ENA) signal to TDObuffer 118. In response to an instruction scan operation, theinstruction register inputs data from TDI and outputs data to TDO viamultiplexer 114, R 116, and TDO buffer 118.

During data scan operations, the TSM outputs a bus of data registercontrol (DRC) signals 120 to a selected data register via DRC router110, the SEL signal to multiplexer 114, the ENA signal to TDO buffer118. In response to a data scan operation, the selected data registerinputs data from TDI and outputs data to TDO via multiplexer 112 andmultiplexer 114, R 116, and TDO buffer 118.

In the FIG. 1 example, a data register is selected for access by dataregister enable (DRE) signals output from the instruction register. TheDRE signals are set by the instruction loaded into the instructionregister. The DRE signals are input to the DRC router to couple the DRCsignal outputs 120 from the TSM to the DRC signal inputs 122,124 of theselected data register. The DRE signals also control multiplexer 112 tocouple the output of the selected data register to the TDO signal viamultiplexer 114, R 116 and TDO buffer 118.

FIG. 2 illustrates the state diagram of the TSM 104 which is well knownin the art. The state diagram has a Test Logic Reset state 202, RunTest/Idle state 204, data register scanning states 206 (Capture-DR,Shift-DR, Exit1-DR, Pause-DR, Exit2-DR and Update-DR) and instructionregister scanning states 208 (Capture-IR, Shift-IR, Exit1-IR, Pause-IR,Exit2-IR and Update-IR). State transitions occur in response to the TMSsignal on the rising edge of the TCK signal. The data scanning statesare entered via the Select-DR state 210 and the instruction scanningstates are entered via the Select-IR state 212.

In the Capture-DR state the selected data register captures data fromits parallel inputs. In the Shift-DR state the selected data registershifts data from TDI to TDO. In the Pause-DR state the selected dataregister pauses shifting. In the Update-DR state the selected dataregister updates data to its parallel outputs.

In the Capture-IR state the instruction register captures data from itsparallel inputs. In the Shift-IR state the instruction register shiftsdata from TDI to TDO. In the Pause-IR state the instruction registerpauses shifting. In the Update-IR state the instruction register updatesdata to its parallel outputs.

FIG. 3 illustrates two known types of DRC signal output groups 302, 304of the TSM DRC signal bus 120. DRC output group 302, comprising ClockDR,ShiftDR and UpdateDR signals, is used to control scan access toasynchronous data registers 108. In this disclosure asynchronous dataregisters are registers comprising scan cells that do not have theability to hold their present state when no capture, shift or updateoperations are taking place. Thus they must be timed by a gated clockinput (i.e. ClockDR). The ClockDR signal is a gated TCK clock signalthat is active in the Capture-DR and Shift-DR TSM states of FIG. 2 . TheShiftDR signal controls the selected data register to capture data inthe Capture-DR state and shift data in the Shift-DR state. The UpdateDRsignal is a gated clock output that is active in the Update-DR state toupdate data from the parallel outputs of the selected data register.

DRC output group 304, comprising a Capture signal, a Shift signal and anUpdate signal, is used to control scan access to synchronous dataregisters 108. In this disclosure synchronous data registers areregisters comprising scan cells that do have the ability to hold theirpresent state when no capture, shift or update operations are takingplace. Thus they can be timed by a free running clock (i.e. TCK). TheCapture signal is set when the TSM is in the Capture-DR state of FIG. 2to cause the data register to capture data from its parallel inputs onthe rising edge of the free running TCK signal. The Shift signal is setwhen the TSM is in the Shift-DR state of FIG. 2 to cause the dataregister to shift data on the rising edge of the free running TCKsignal. The Update signal is set when the TSM is in the Update-DR stateof FIG. 2 to cause the data register to update data to its paralleloutputs on the falling edge of the free running TCK signal.

While not shown, the IRC signals from TSM 104 may use similar groups ofsignals for performing capture, shift and update operations onasynchronous or synchronous types of instruction registers 106.

FIG. 4 illustrates the DRC router 110 in more detail. In this example,the DRC router 110 is used to couple the DRC bus signals 120 of TSM 104to four types of data registers, (1) an asynchronous capture, shift andupdate (CSU) data register 410, (2) an asynchronous capture and shift(CS) data register 412, (3) a synchronous capture, shift and update(CSU) data register 414 and (4) a synchronous capture and shift (CS)data register 416. As will be shown in example FIGS. 9 and 10 , the CSUdata registers 410 and 414 include an update register that is coupled tothe parallel outputs of the shift register of the data register. As willbe shown in example FIGS. 13 and 14 , the CS data registers 412 and 416only include a shift register with parallel outputs.

When scan access to data register 410 is required, a first instructionis scanned into the instruction register 106 to output DRE controlsignals that enable routing circuit 402 to; (1) couple the ClockDRsignal of bus 120 to the ClockDR signal input of data register 410, (2)couple the ShiftDR signal of bus 120 to the ShiftDR signal input of dataregister 410, (3) couple the UpdateDR signal of bus 120 to the UpdateDRsignal input of data register 410

When scan access to data register 412 is required, a second instructionis scanned into the instruction register 106 to output DRE controlsignals that enable routing circuit 404 to; (1) couple the ClockDRsignal of bus 120 to the ClockDR signal input of data register 412 and(2) couple the ShiftDR signal of bus 120 to the ShiftDR signal input ofdata register 412.

When scan access to data register 414 is required, a third instructionis scanned into the instruction register 106 to output DRE controlsignals that enable routing circuit 406 to; (1) couple the Capturesignal of bus 120 to the Capture signal input of data register 414, (2)couple the Shift signal of bus 120 to the Shift signal input of dataregister 414, (3) couple the Update signal of bus 120 to the Updatesignal input of data register 414. Data register 414 is clocked by thefree running TCK signal.

When scan access to data register 416 is required, a fourth instructionis scanned into the instruction register 106 to output DRE controlsignals that enable routing circuit 408 to; (1) couple the Capturesignal of bus 120 to the Capture signal input of data register 416 and(2) couple the Shift signal of bus 120 to the Shift signal input of dataregister 416. Data register 416 is clocked by the free running TCKsignal.

Routing circuits 402-408 that are not enabled by the current instructionin the instruction register will decouple their outputs from the DRC bussignals 120 and set their outputs to static desired states.

FIG. 5 illustrates a simplified view of a TAP within a device 502 thathas a data register 108 that has been enabled for scan access by the DREsignals from instruction register (IR) 106. The simplified view of FIG.5 and other Figures to follow does not show multiplexers 112 and 114, R116, or TDO buffer 118 between the data register output and TDO, butthey are assumed to exist. The data register 108 can be any type of dataregister or similar type circuit including but not limited too, anasynchronous CSU data register 410, an asynchronous CS data register, asynchronous CSU data register 414, a synchronous CS data register 416 ora test compression architecture having a compressed data input coupledto TDI and a compressed data output coupled to TDO.

FIG. 6 illustrates the scan access timing of accessing a CSU type dataregister 108. As seen, the scan access timing is controlled by the TSM104 repeatedly transitioning through the Select-DR, Capture-DR,Shift-DR, Exit1-DR and Update-DR states of FIG. 2 . The data registerperforms a data Capture operation (OP) on the rising edge of the TCKwhen the TSM is in the Capture-DR state. The data register performs adata Shift operation (OP) on the rising edge of the TCK when the TSM isin the Shift-DR state. The data register performs a data Updateoperation (OP) on the falling edge of the TCK when the TSM is in theUpdate-DR state.

FIG. 7 illustrates the scan access timing of accessing a CS type dataregister 108. As seen, the scan access timing is controlled by the TSM104 repeatedly transitioning through the Select-DR, Capture-DR,Shift-DR, Exit1-DR and Update-DR states of FIG. 2 . The data registerperforms a data Capture operation on the rising edge of the TCK when theTSM is in the Capture-DR state. The data register performs a data Shiftoperation on the rising edge of the TCK when the TSM is in the Shift-DRstate. The data register does not perform a data Update operation on thefalling edge of the TCK when the TSM is in the Update-DR state since ithas no update register.

FIG. 8A is provided to illustrate that the data register 108 of FIG. 5could be a test data register 802 coupled to circuitry to be tested,such as but not limited too combination logic and memories.

FIG. 8B is provided to illustrate that the data register 108 of FIG. 5could be a debug data register 804 coupled to circuitry to be debugged,such as but not limited too microcontrollers and DSPs.

FIG. 8C is provided to illustrate that the data register 108 of FIG. 5could be a programming data register 806 coupled to circuitry to beprogrammed, such as but not limited too FPGAs, CPLDs and memories(Flash/PROM) as described in IEEE standard 1532.

FIG. 8D is provided to illustrate that the data register 108 of FIG. 5could be a Instrumentation data register 808 coupled to instrumentationcircuitry embedded within a device, such as but not limited tooinstrumentation circuitry described in IEEE standard P1687.

FIG. 8E is provided to illustrate that the data register 108 of FIG. 5could be an IC boundary register 810 coupled to the IC interconnects forthe purpose of testing the IC interconnects as described in IEEEstandards, 1149.1, 1149.4, 1149.6, and P1149.8.1 and shown in FIG. 8I.

FIG. 8F is provided to illustrate that the data register 108 of FIG. 5could be an IC boundary register 812 of an IC coupled to the IC systemlogic for the purpose of testing the system logic as described in IEEEstandard 1149.1 and shown in FIG. 8J.

FIG. 8G is provided to illustrate that the data register 108 of FIG. 5could be a core wrapper boundary register 814 coupled to the coreinterconnects for the purpose of testing the core interconnects asdescribed in IEEE standard 1500 and shown in FIG. 8I.

FIG. 8H is provided to illustrate that the data register 108 of FIG. 5could be a core wrapper boundary register 816 coupled to the core systemlogic for the purpose of testing the system logic as described in IEEEstandard 1500 and shown in FIG. 8J.

FIG. 8I illustrates how the IC boundary register 810 could be used totest the interconnects between two ICs according to IEEE 1149.1 and howthe core wrapper boundary register 814 could be used to test theinterconnects between two cores in an IC according to IEEE 1500.

FIG. 8J illustrates how the IC boundary registers 814 could be used totest the system logic of an IC according to IEEE 1149.1 and how the corewrapper boundary register 816 could be used to test the system logic ofa core in an IC according to IEEE 1500.

FIG. 9 illustrates an example asynchronous CSU data register 902 coupledto TSM 104 via a routing circuit 906 located within DRC router 110 ofFIG. 4 . Data register 902 could be, but is not limited to being, theIEEE 1149.1 IC boundary register of FIGS. 8E and 8F or the IEEE 1500core wrapper boundary register of FIG. 8G or 8H. When the routingcircuit 906 is enabled by DRE inputs from the instruction register 106,the ClockDR, ShiftDR and UpdateDR signals from the TSM pass through therouting circuit to operate CSU scan cells 904 within data register 902.

FIG. 10 illustrates the CSU scan cell 904 which comprises a multiplexer1002, a shift register FF 1004, an update register FF 1006 andoptionally a multiplexer 1008. When the TSM is in the Capture-DR stateof FIG. 2 , multiplexer 1002 will be set by the ShiftDR signal to couplethe scan cell's data input (DI) to FF 1004 to allow the DI to becaptured into FF 1004 in response to a clock input on ClockDR. When theTSM is in the Shift-DR state of FIG. 2 , multiplexer 1002 will be set bythe ShiftDR signal to couple the TDI signal to FF 1004 to allow TDI datato be shifted into FF 1004 and TDO data to be shifted out of FF 1004 inresponse to clock inputs on ClockDR. When the TSM is in the Update-DRstate of FIG. 2 , FF 1006 will update (load) with the data output fromFF 1004 in response to a clock input on UpdateDR and outputs the data onthe scan cell's data output (DO). If the scan cell 904 does not includemultiplexer 1008 the DO from update FF 1006 will pass directly to DO1010. If the scan cell 904 includes multiplexer 1008 the DO from updateFF 1006 will pass to DO 1012 via multiplexer 1008. When scan cell 904includes the multiplexer 1008 it operates as an IEEE 1149.1 boundaryscan cell which allows DO 1012 to be selectively driven by DI or by theoutput of update FF 1006 in response to a Mode signal input from the DREbus. Including multiplexer 1008 supports boundary scan testing on theinterconnects between devices as shown in FIG. 8I

FIG. 11 illustrates routing circuit 906 which comprises a gating circuit1102, a gating circuitry 1104, a gating circuitry 1106 and optionally aclock multiplexer 1108 as shown in FIG. 12 . When routing circuit 906 isenable by DRE signal inputs, the ClockDR signal from TSM 104 is routedto the ClockDR input of data register 902, the ShiftDR signal from TSM104 is routed to the ShiftDR input of data register 902, and theUpdateDR signal from TSM 104 is routed to the UpdateDR input of dataregister 902. When the routing circuit 906 is disabled by DRE signalinputs, the gating circuits 1102-1106 isolate the TSM ClockDR, ShiftDRand UpdateDR outputs from the data register ClockDR, ShiftDR andUpdateDR inputs and sets the ClockDR, ShiftDR and UpdateDR inputs to thedata register to static desired states. If clock multiplexer 1108 isincluded in the routing circuit 906, it will be controlled by a DREinput to select the ClockDR input to the data register 902 to be drivenby either the ClockDR output of gating circuit 1102 during test mode orby a functional clock (FC) signal during non-test mode, i.e. duringfunctional device operation mode.

The Gating circuits of FIG. 11 and following Figures of this disclosurecan be any type of gating circuitry required to control the dataregister inputs to the appropriate signal levels during test and duringfunctional operation modes.

FIG. 13 illustrates an example asynchronous CS data register 1302coupled to TSM 104 via a routing circuit 1306 located within DRC router110 of FIG. 4 . When the routing circuit 1306 is enabled by DRE inputsfrom the instruction register 106, the ClockDR and ShiftDR signals fromthe TSM pass through the routing circuit to operate CS scan cells 1304within data register 1302. Data register 1302 could be, but is notlimited to being, the test data register of FIG. 8A for testingcircuitry coupled to the DI input and DO output of the scan cells 1304.The FF 1404 of the scan cells 1304 is typically shared betweenfunctional and test operations.

FIG. 14 illustrates the CS scan cell 1304 which comprises a multiplexer1402 and shift register FF 1404. When the TSM is in the Capture-DR stateof FIG. 2 , multiplexer 1402 will be set by the ShiftDR signal to couplethe scan cell's data input (DI) to FF 1404 to allow the DI to becaptured into FF 1404 in response to a clock input on ClockDR. When theTSM is in the Shift-DR state of FIG. 2 , multiplexer 1402 will be set bythe ShiftDR signal to couple the TDI signal to FF 1404 to allow TDI datato be shifted into FF 1404 and TDO data to be shifted out of FF 1404 inresponse to clock inputs on ClockDR. As seen the data output from FF1404 is output on the scan cell's DO and TDO output.

FIG. 15 illustrates routing circuit 1306 which comprises a gatingcircuit 1502, a gating circuitry 1504 and optionally the previouslydescribe clock multiplexer 1108 of FIG. 12 . When routing circuit 1306is enable by DRE signal inputs, the ClockDR signal from TSM 104 isrouted to the ClockDR input of data register 1302 and the ShiftDR signalfrom TSM 104 is routed to the ShiftDR input of data register 1302. Whenthe routing circuit 906 is disable by DRE signal inputs, the gatingcircuits 1502-1504 isolate the TSM ClockDR and ShiftDR outputs from thedata register ClockDR and ShiftDR inputs and sets the ClockDR andShiftDR inputs to the data register to static desired states. If clockmultiplexer 1108 is included in the routing circuit 1306, it will becontrolled by a DRE input to select the ClockDR input to the dataregister 902 to be driven by either the ClockDR output of gating circuit1502 during test mode or by a FC during non-test mode.

FIG. 16 illustrates an example synchronous CSU data register 1602coupled to TSM 104 via a routing circuit 1606 located within DRC router110 of FIG. 4 . Data register 1602 could be, but is not limited tobeing, the IEEE 1149.1 IC boundary register of FIGS. 8E and 8F or theIEEE 1500 core wrapper boundary register of FIGS. 8G and 8H. When therouting circuit 1606 is enable by DRE inputs from the instructionregister 106, the Capture, Shift and Update signals from the TSM passthrough the routing circuit to operate CSU scan cells 1604 within dataregister 1602.

FIG. 17 illustrates the CSU scan cell 1604 which comprises a multiplexer1702, a shift register FF 1704, a multiplexer 1706, an update registerFF 1708 and optionally a multiplexer 1710. When the TSM is in theCapture-DR state of FIG. 2 , multiplexer 1702 will be set by the Captureand Shift signals to couple the scan cell's data input (DI) to FF 1704to allow the DI to be captured into FF 1704 in response to the freerunning TCK signal. When the TSM is in the Shift-DR state of FIG. 2 ,multiplexer 1702 will be set by the Capture and Shift signals to couplethe TDI signal to FF 1704 to allow TDI data to be shifted into FF 1704and TDO data to be shifted out of FF 1704 in response to the freerunning TCK signal. When the TSM is not in either the Capture-DR orShift-DR state, multiplexer 1702 couples the output of FF 1704 to theinput of FF 1704 causing FF 1704 to hold its present state in responseto TCK inputs. When the TSM is in the Update-DR state of FIG. 2 , FF1708 will update (load) with the data output from FF 1704 in response tothe free running TCK input and output the data on the scan cell's dataoutput (DO). If the scan cell 1604 does not include multiplexer 1710 theDO from update FF 1708 will pass directly to DO 1714. If the scan cell1604 includes multiplexer 1710 the DO from update FF 1708 will pass toDO 1712 via multiplexer 1710. When scan cell 1604 includes themultiplexer 1710 it operates as an IEEE 1149.1 or IEEE 1500 boundaryscan cell which allows DO 1712 to be selectively driven by DI or by theoutput of update FF 1708 in response to a Mode signal input from the DREbus. Including multiplexer 1710 supports boundary scan testing on theinterconnects between devices as shown in FIG. 8I

FIG. 18 illustrates routing circuit 1606 which comprises a gatingcircuit 1802, a gating circuitry 1804 and a gating circuitry 1806. Whenrouting circuit 1606 is enable by DRE signal inputs, the Capture signalfrom TSM 104 is routed to the Capture input of data register 1602, theShift signal from TSM 104 is routed to the Shift input of data register1602, and the Update signal from TSM 104 is routed to the Update inputof data register 1602. When the routing circuit 1602 is disable by DREsignal inputs, the gating circuits 1802-1806 isolate the TSM Capture,Shift and Update outputs from the data register Capture, Shift andUpdate inputs and sets the Capture, Shift and Update inputs to the dataregister to static desired states.

As seen in FIG. 16 , a clock multiplexer 1608 as shown in FIG. 16A canbe included in the TCK path to the scan cells of data register 1602. Ifincluded, the clock multiplexer can be controlled by a DRE input toselect the TCK input to the scan cells to be driven by either the TCKsignal during test mode or by a FC during non-test mode.

FIG. 19 illustrates an example synchronous CS data register 1902 coupledto TSM 104 via a routing circuit 1906 located within DRC router 110 ofFIG. 4 . When the routing circuit 1906 is enable by DRE inputs from theinstruction register 106, the Capture and Shift signals from the TSMpass through the routing circuit to operate CS scan cells 1904 withindata register 1902. Data register 1902 could be, but is not limited tobeing, the test data register of FIG. 8A for testing circuitry coupledto the DI input and DO output of the scan cells 1904.

FIG. 20 illustrates the CS scan cell 1904 which comprises a multiplexer2002 and shift register FF 2004. When the TSM is in the Capture-DR stateof FIG. 2 , multiplexer 2002 will be set by the Capture and Shiftsignals to couple the scan cell's data input (DI) to FF 2004 to allowthe DI to be captured into FF 2004 in response to the free running TCKsignal. When the TSM is in the Shift-DR state of FIG. 2 , multiplexer2002 will be set by the Capture and Shift signals to couple the TDIsignal to FF 2004 to allow TDI data to be shifted into FF 2004 and TDOdata to be shifted out of FF 2004 in response to the free running TCKsignal. When the TSM is not in either the Capture-DR or Shift-DR state,multiplexer 2002 couples the output of FF 2004 to the input of FF 2004causing FF 2004 to hold its present state in response to TCK inputs. Asseen the data output from FF 2004 is output on the scan cell's DO andTDO output.

FIG. 21 illustrates routing circuit 1906 which comprises a gatingcircuit 2102 and gating circuitry 2104. When routing circuit 1906 isenable by DRE signal inputs, the Capture signal from TSM 104 is routedto the Capture input of data register 1902 and the Shift signal from TSM104 is routed to the Shift input of data register 1902. When the routingcircuit 1902 is disable by DRE signal inputs, the gating circuits2102-2104 isolate the TSM Capture and Shift outputs from the dataregister Capture and Shift inputs and sets the Capture and Shift inputsto the data register to static desired states.

As seen in FIG. 19 , clock multiplexer 1608 shown and described inregard to FIGS. 16 and 16A can be included in the TCK path to the scancells of data register 1902 to allow the scan cells to be driven byeither the TCK signal during test mode or by a FC during non-test mode.

FIG. 22 illustrates an example test compression architecture (TCA) 2202within a device coupled to a TSM 104 via routing circuit 1306. TCAarchitectures are well known, such as but not limited to Mentor'sTestKompress™ architecture. The example TCA comprises a decompressorcircuit 2204, parallel scan paths 2206, and a compactor circuit 2208.Each scan path comprises scan cells as described in FIGS. 13 and 14 .The TCA of FIG. 22 , while significantly more complex in construction,can be operated in basically the same way as the asynchronous dataregister 1302 of FIG. 13 by coupling the TSM 104 to the TCA via routingcircuit 1306. The decompressor circuit operates to input compressed testdata from TDI and decompress the test data into individual stimulus datainputs to the scan paths. The compactor circuit operates to inputindividual outputs from the scan paths and compact them down to acompressed test data output signal on TDO.

When routing circuit 1306 is enabled by DRE inputs from the instructionregister 106, the ClockDR and ShiftDR signals from the TSM pass throughthe routing circuit to operate the decompressor, scan paths andcompactor circuits to perform capture and shift operations as describedin regard to the data register 1302 of FIGS. 13, 14 and 15 . When theTSM is in the Capture-DR state of FIG. 2 , the ClockDR and ShiftDRsignals are operated to perform a capture operation which loads responsedata from combinational logic associated with the scan paths andinitializes the decompressor circuit 2204 to receive a stream ofcompressed test data from TDI. When the TSM is in the Shift-DR state ofFIG. 2 , the ClockDR and ShiftDR signals are operated to perform a shiftoperation which shifts stimulus data from the decompressor circuit intothe scan paths and shifts response data from the scan paths into thecompactor circuit. The response data input to the compactor circuitduring the shift operation is compacted down to a single stream ofcompressed test data output on the TDO signal.

As seen in FIG. 22 , clock multiplexer 1108 shown and described inregard to FIGS. 11 and 12 can be included in the ClockDR path to thescan cells of the scan paths 2206 to allow the scan cells to be drivenby either the ClockDR signal during test mode or by a FC during non-testmode.

FIG. 23 illustrates another example test compression architecture (TCA)2202 within a device coupled to a TSM 104 via routing circuit 1906. Theexample TCA comprises a decompressor circuit 2304, parallel scan paths2306, and a compactor circuit 2308. Each scan path comprises scan cellsas described in FIGS. 19 and 20 . The TCA of FIG. 23 , whilesignificantly more complex in construction, can be operated in basicallythe same way as the synchronous data register 1902 of FIG. 19 bycoupling the TSM 104 to the TCA via routing circuit 1306. Thedecompressor circuit operates to input compressed test data from TDI anddecompress the test data into individual stimulus data inputs to thescan paths. The compactor circuit operates to input individual outputsfrom the scan paths and compact them down to a compressed test dataoutput signal on TDO.

When routing circuit 1906 is enabled by DRE inputs from the instructionregister 106, the Capture and Shift signals from the TSM pass throughthe routing circuit to operate the decompressor, scan paths andcompactor circuits to perform capture and shift operations as describedin regard to the data register 1902 of FIGS. 19, 20 and 21 . When theTSM is in the Capture-DR state of FIG. 2 , the Capture, Shift and TCKsignals operate to perform a capture operation which loads response datafrom combinational logic associated with the scan paths and initializesthe decompressor circuit 2304 to receive a stream of compressed testdata from TDI. When the TSM is in the Shift-DR state of FIG. 2 , theCapture, Shift and TCK signals operate to perform a shift operationwhich shifts stimulus data from the decompressor circuit into the scanpaths and shifts response data from the scan paths into the compactorcircuit. The response data input to the compactor circuit during theshift operation is compacted down to a single stream of compressed testdata output on the TDO signal.

As seen in FIG. 23 , clock multiplexer 1608 shown and described inregard to FIGS. 16 and 19 can be included in the TCK path to the scancells of the scan paths 2306 to allow the scan cells to be driven byeither the TCK signal during test mode or by a FC signal during non-testmode.

BRIEF SUMMARY OF THE DISCLOSURE

This disclosure describes a method and apparatus for allowing a TAPwithin a device to control data registers or other elements, such as butnot limited to test compression architectures (TCA), to performuninterrupted capture and shift operations or capture, shift and updateoperations in response to a command signal.

BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS

FIG. 1 illustrates a conventional Test Access Port (Tap) architecture ina device.

FIG. 2 illustrates the state diagram of the Tap state machine (TSM) inthe Tap architecture.

FIG. 3 illustrates the data register control (DRC) outputs of a Tapstate machine.

FIG. 4 illustrates a conventional arrangement between a TSM, DRC router,and data registers of a device.

FIG. 5 illustrates a simplified view of the TSM, DRC router and dataregister.

FIG. 6 illustrates a conventional TSM controlled update, capture andshift operation.

FIG. 7 illustrates a conventional TSM controlled capture and shiftoperation.

FIG. 8A illustrates a data register being a test data register.

FIG. 8B illustrate a data register being debug data register.

FIG. 8C illustrates a data register being a programming data register.

FIG. 8D illustrates a data register being an instrumentation dataregister.

FIG. 8E illustrates a data register being an IC boundary register fortesting IC interconnects.

FIG. 8F illustrates a data register being an IC boundary register fortesting IC system logic.

FIG. 8G illustrates a data register being a core wrapper boundaryregister for testing core interconnects.

FIG. 8H illustrates a data register being a core wrapper boundaryregister for testing core system logic.

FIG. 8I illustrates boundary registers testing interconnects betweencores or ICs.

FIG. 8J illustrates boundary registers testing system logic in a core orIC.

FIG. 9 illustrates a conventional TSM, routing circuit and data registerarrangement.

FIG. 10 illustrates the scan cells of the data register of FIG. 9 .

FIG. 11 illustrates the routing circuit of FIG. 9 .

FIG. 12 illustrates a clock multiplexing circuit.

FIG. 13 illustrates a conventional TSM, routing circuit and dataregister arrangement.

FIG. 14 illustrates the scan cells of the data register of FIG. 13 .

FIG. 15 illustrates the routing circuit of FIG. 13 .

FIG. 16 illustrates a conventional TSM, routing circuit and dataregister arrangement.

FIG. 16A illustrates a clock multiplexer circuit

FIG. 17 illustrates the scan cells of the data register of FIG. 16 .

FIG. 18 illustrates the routing circuit of FIG. 16 .

FIG. 19 illustrates a conventional TSM, routing circuit and dataregister arrangement.

FIG. 20 illustrates the scan cells of the data register of FIG. 19 .

FIG. 21 illustrates the routing circuit of FIG. 19 .

FIG. 22 illustrates an example TSM, routing circuit and test compressionarchitecture arrangement.

FIG. 23 illustrates an example TSM, routing circuit and test compressionarchitecture arrangement.

FIG. 24 illustrates an arrangement between a TSM, commandable DRCrouter, and data registers of a device according to the disclosure.

FIG. 25A illustrates a simplified view of the TSM, commandable DRCrouter and data register according to the disclosure.

FIG. 25B illustrates a commanded update, capture and shift operationaccording to the disclosure.

FIG. 25C illustrates a commanded capture and shift operation accordingto the disclosure.

FIG. 26A illustrates an alternate simplified view of the TSM,commandable DRC router and data register according to the disclosure.

FIG. 26B illustrates an alternate commanded update, capture and shiftoperation according to the disclosure.

FIG. 26C illustrates an alternate commanded capture and shift operationaccording to the disclosure.

FIG. 27A illustrates a first example CMD circuit according to thedisclosure.

FIG. 27B illustrates a second example CMD circuit according to thedisclosure.

FIG. 27C illustrates a third example CMD circuit according to thedisclosure.

FIG. 27D illustrates a fourth example CMD circuit according to thedisclosure.

FIG. 28 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 29 illustrates the commandable DRC router of FIG. 28 .

FIG. 30 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 31 illustrates the commandable DRC router of FIG. 30 .

FIG. 32 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 33 illustrates the commandable DRC router of FIG. 32 .

FIG. 34 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 35 illustrates the commandable DRC router of FIG. 34 .

FIG. 36 illustrates a TSM, commandable DRC router and test compressionarchitecture arrangement according to the disclosure.

FIG. 37 illustrates an alternate TSM, commandable DRC router and testcompression architecture arrangement according to the disclosure.

FIG. 38 illustrates an alternate TSM, commandable DRC router and dataregister arrangement according to the disclosure.

FIG. 39 illustrates the commandable DRC router of FIG. 38 .

FIG. 40 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 41 illustrates the commandable DRC router of FIG. 40 .

FIG. 42 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 43 illustrates the commandable DRC router of FIG. 42 .

FIG. 44 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 45 illustrates the commandable DRC router of FIG. 44 .

FIG. 46 illustrates a TSM, commandable DRC router and data registerarrangement according to the disclosure.

FIG. 47 illustrates the scan cells of the data register of FIG. 46 .

FIG. 48 illustrates the commandable DRC router of FIG. 46 .

FIG. 49 illustrates a TSM, commandable DRC router and test compressionarchitecture arrangement according to the disclosure.

FIG. 50 illustrates an alternate TSM, commandable DRC router and testcompression architecture arrangement according to the disclosure.

FIG. 51 illustrates an alternate TSM, commandable DRC router and dataregister arrangement according to the disclosure.

FIG. 52 illustrates a Tap architecture containing both a DRC router anda commandable DRC router according to the disclosure.

FIG. 53A illustrates a device with a conventional Tap connected to acontroller.

FIG. 53B illustrates the conventional Tap of FIG. 53A performing anupdate, capture and shift operation.

FIG. 54A illustrates a device with a commandable Tap connected to acontroller according to the disclosure.

FIG. 54B illustrates the commandable Tap of FIG. 54A performing anupdate, capture and shift operation according to the disclosure.

FIG. 55A illustrates a device with a conventional Tap connected to acontroller.

FIG. 55B illustrates the conventional Tap of FIG. 55A performing acapture and shift operation.

FIG. 56A illustrates a device with a commandable Tap connected to acontroller according to the disclosure.

FIG. 56B illustrates the commandable Tap of FIG. 56A performing acapture and shift operation according to the disclosure.

FIG. 57A illustrates a daisy chain of devices with conventional Tapsconnected to a controller.

FIG. 57B illustrates the conventional Taps of FIG. 57A performing anupdate, capture and shift operation.

FIG. 58A illustrates a daisy chain of devices with commandable Tapsconnected to a controller according to the disclosure.

FIG. 58B illustrates the commandable Taps of FIG. 58A performing anupdate, capture and shift operation according to the disclosure.

FIG. 59A illustrates a daisy chain of devices connected to a controller.

FIG. 59B illustrates the devices of FIG. 59A performing a conventionalupdate, capture and shift operation.

FIG. 59C illustrates the devices of FIG. 59A performing a conventionalcapture and shift operation.

FIG. 60A illustrates a daisy chain of devices connected to a controller.

FIG. 60B illustrates the devices of FIG. 60A performing a conventionalupdate, capture and shift operation.

FIG. 60C illustrates the devices of FIG. 60A performing a conventionalcapture and shift operation.

FIG. 61A illustrates a daisy chain of devices connected to a controller.

FIG. 61B illustrates the devices of FIG. 61A performing a conventionalupdate, capture and shift operation.

FIG. 61C illustrates the devices of FIG. 61A performing a conventionalcapture and shift operation.

FIG. 62A illustrates a daisy chain of devices connected to a controller.

FIG. 62B illustrates the devices of FIG. 62A performing an update,capture and shift operation according to the disclosure.

FIG. 62C illustrates the devices of FIG. 62A performing a capture andshift operation according to the disclosure.

FIG. 63A illustrates a daisy chain of devices connected to a controller.

FIG. 63B illustrates the devices of FIG. 63A performing an update,capture and shift operation according to the disclosure.

FIG. 63C illustrates the devices of FIG. 63A performing a capture andshift operation according to the disclosure.

FIG. 64A illustrates a daisy chain of devices connected to a controller.

FIG. 64B illustrates the devices of FIG. 64A performing an update,capture and shift operation according to the disclosure.

FIG. 64C illustrates the devices of FIG. 64A performing a capture andshift operation according to the disclosure.

FIG. 65 illustrates the timing of a back to back capture and shiftoperation according to the disclosure.

FIG. 66 illustrates a command circuit that can be programmed to controla capture and shift operation or a back to back capture and shiftoperation according to the disclosure.

FIG. 67A illustrates a device with a conventional Tap in series with adevice with a commandable Tap according to the disclosure.

FIG. 67B illustrate the TCK and TMS timing to operate the devices ofFIG. 67A conventionally.

FIG. 68A illustrates a device with a conventional Tap in series with adevice with a commandable Tap according to the disclosure.

FIG. 68B illustrate the TCK and TMS timing to operate the devices ofFIG. 68A in the commandable mode of the disclosure.

FIG. 69 illustrates a device with parallel scan paths and a commandableTap connected to a tester according to the disclosure.

FIG. 70 illustrates a device with a parallel input parallel output testcompression architecture and a commandable Tap connected to a testeraccording to the disclosure.

FIG. 71A illustrates a device with a commandable Tap that uses aseparate command signal to input commands according to the disclosure.

FIG. 71B illustrates the device of FIG. 71A performing an update,capture and shift operation in response to command input on the separatecommand signal according to the disclosure.

FIG. 71C illustrates the device of FIG. 71A performing a capture andshift operation in response to command input on the separate commandsignal according to the disclosure.

FIG. 72A illustrates a device with a commandable Tap that uses aseparate command signal to input commands according to the disclosure.

FIG. 72B illustrates the commandable DRC router (CDR) of FIG. 72A.

FIG. 73 illustrates the devices of FIGS. 72A and 74A performing acapture and shift operation in response to command input on the separatecommand signal according to the disclosure.

FIG. 74A illustrates a device with a commandable Tap that uses aseparate command signal to input commands according to the disclosure.

FIG. 74B illustrates the commandable DRC router (CDR) of FIG. 74A.

FIG. 75A illustrates a device with a commandable Tap that uses aseparate command signal to input commands according to the disclosure.

FIG. 75B illustrates the commandable DRC router (CDR) of FIG. 75A.

FIG. 76A illustrates a device with a commandable Tap that uses aseparate command signal to input commands according to the disclosure.

FIG. 76B illustrates the commandable DRC router (CDR) of FIG. 76A.

FIG. 77 illustrates a controller connected to device that includes acommandable Tap and a separate command signal input according to thedisclosure.

FIG. 78 illustrates a controller connected to a daisy chain of devicesthat include commandable Taps and separate command signal inputsaccording to the disclosure.

FIG. 79 illustrates a controller connected to a daisy chain of devicesthat include conventional Taps and devices that include commandable Tapswith separate command signal inputs according to the disclosure.

DETAILED DESCRIPTION OF THE DISCLOSURE

FIG. 24 illustrates an example commandable DRC router 2402 according tothe disclosure which comprises routing circuits 2406-2412 and a command(CMD) circuit 2404. The CMD circuit has inputs coupled to the TCKsignal, TMS signal and the Shift signal of bus 120. The CMD circuit hascontrol output signals C1 and C2 coupled to first inputs of routingcircuits 2406-2412. While this example CMD circuit 2404 uses two controloutput signals C1 and C2, a CMD circuit 2404 may use any number ofcontrol output signals. Second inputs of routing circuits 2406-2412 arecoupled to the DRC bus signals of TSM 104. The routing circuits2406-2412 can be used to couple the TSM DRC bus signals 120 to the fourtypes of data registers 410-416 for conventional TSM control asdescribed in regard to FIG. 4 and other preceding Figures, or therouting circuits 2406-2412 can be used to couple the control signals (C1and C2) of CMD circuit 2404 to the data register 410-416 for the newcontrol method to be described in this disclosure. While not shown, theTCAs of FIGS. 22 and 23 can be similarly coupled to the TSM DRC bussignals 120 for conventional control or to the control signals (C1 andC2) of the CMD circuit 2404 for the new control method of thedisclosure.

When conventional scan access to one of the data registers 410-416 isrequired, an instruction is scanned into the instruction register 106 tooutput DRE control signals that enable the associated commandablerouting circuit 2402-2412 to couple the appropriate TSM DRC bus signalsto the target data register. Once the TSM is coupled to the target dataregister via the commandable DRC router, the TSM is operated totransition through the states FIG. 2 to perform scan access cycles asshown in FIGS. 6 and 7 .

When scan access to one of the data registers 410-416 is required usingthe new control method of the disclosure, an instruction is scanned intothe instruction register 106 to output DRE control signals that enablean associated commandable routing circuit 2402-2412 to couple theappropriate C1 and C2 signals of CMD circuit 2404 to the target dataregister. Once the C1 and C2 signal of the CMD circuit are coupled tothe target data register via the commandable DRC router, the TSM istransitioned to the Shift-DR state of FIG. 2 which asserts the Shiftsignal to enable the CMD circuit to respond to a command input on theTMS signal in response to the TCK signal to output C1 and C2 controlsignals to the target data register to perform scan operations.

Commandable routing circuits 2406-2412 that are not enabled by thecurrent instruction in the instruction register will decouple theiroutputs from the TSM DRC bus signals 120 and CMD circuit C1 and C2signals and set their outputs to static desired states.

FIG. 25A illustrates a commandable DRC router 2402 comprising CMDcircuit 2404 and a routing circuit 2502. The commandable DRC router 2402is located between a TSM 104 and a data register 108. The data register108 may be a CSU data register or a CS data register. The commandableDRC router 2402 has a DRC input bus 120 from TSM 104 that is input toCMD circuit 2404 and routing circuit 2502 and a DRC output bus 2504 thatis output from the routing circuit 2502 to the data register 108. TheCMD circuit 2404 may optionally be coupled to the DRE signal bus, asshown in dotted line, to allow it to be programmable via the DRE inputas shown in FIG. 27B. The routing circuit 2502 may optionally beconnected to the TCK signal, as shown in dotted line, to allow TCK totime some of the DRC bus signals 2504.

When scan access to the data register is desired using conventional DRCcontrol from the TSM, an instruction is loaded into the instructionregister 106 to output DRE control to the routing circuit 2502 to causeappropriate bus signals from DRC input bus 120 to be coupled to DRCoutput bus signals 2504. After the DRC input bus 120 is coupled to theDRC output 2504 the TSM 104 can be operated through its states as shownin the timing diagrams of FIGS. 6 and 7 to perform scan access to thedata register. During conventional scan access the routing circuit 2502operates as a routing circuit in the DRC router 110 of FIG. 4 .

When scan access to the data register 108 is desired using the newcontrol method of the disclosure, an instruction is be loaded into theinstruction register 106 to output DRE control to the routing circuit2502 to select the C1 and C2 signals from CMD circuit 2402 to controlthe DRC output bus signals 2504. After the C1 and C2 signals areselected to control the DRC output bus 2504 of the routing circuit 2502,the TSM is transitioned to the Shift-DR state of FIG. 2 . In theShift-DR state the data register 108 is enabled for shifting data fromTDI to TDO and the Shift signal of bus 120 is asserted to enable theoperation of the CMD circuit 2404. At appropriate times during theshifting of data, a CMD signal is input to the CMD circuit 2404 from theTMS signal on the falling edge of TCK. In response to the CMD signal theCMD circuit outputs C1 or C1 and C2 control signals to routing circuit2502 to cause the routing circuit to output control on DRC output bus2504 to perform a capture or an update and capture operation on the dataregister 108. The capture or update and capture operation on the dataregister is performed in response to receiving the CMD signal from TMSand while the TSM 104 remains in the Shift-DR state. If the dataregister 108 is a CS data register only the capture operation will beperformed. If the data register 108 is a CSU data register both theupdate and capture operation will be performed. Following the dataregister capture or update and capture operation, the C1 and C2 controlsignals from the CMD circuit are set to allow the data register toresume shifting data from TDI to TDO.

The diagram of FIG. 25B illustrates timing of the above mentionedcapture, shift and update operations occurring on a CSU data register108 that is being controlled by the CMD circuit while the TSM is in theShift-DR state. At time points 2506 the data register is shifting datafrom TDI to TDO on the rising edge of TCK. At time point 2508, the CMDcircuit 2404 receives a CMD input from TMS on the falling edge of TCK.In response to the CMD input, the CMD circuit outputs control to therouting circuit 2502 to cause the routing circuit to output DRC controlon bus 2504 to perform an update operation on the rising edge of TCK attime point 2510 then to perform a capture operation on the next risingedge of TCK at time point 2512. Following the update and captureoperations the data register resumes shifting data from TDI to TDO onthe rising edge of TCK at time point 2514.

It is important to the note in FIG. 25B that the CSU data registerupdate operation 2510 occurs on the next rising edge TCK after the last(Shift-N) rising edge TCK shift operation 2516. This provides an updatetiming improvement over a conventional TSM controlled CSU data registerupdate operation which, as seen in FIG. 6 , occurs one and one half TCKsafter the last shift (Shift-N) operation.

It is also important to the note in FIG. 25B that the CSU data registercapture operation 2512 occurs on the next rising edge TCK after theupdate operation 2510. This provides a capture timing improvement over aconventional TSM controlled CSU data register capture operation which,as seen in FIG. 6 , occurs two and one half TCKs after the updateoperation. The disclosures ability to perform a capture operation oneTCK after an update operation allows testing for circuit timing relatedproblems that cannot be tested using a conventional TSM controlledupdate and capture operation.

The diagram of FIG. 25C illustrates timing of the above mentionedcapture and shift operations occurring on a CS data register 108 that isbeing controlled by the CMD circuit while the TSM is in the Shift-DRstate. At time points 2516 the data register is shifting data from TDIto TDO on the rising edge of TCK. At time point 2518, the CMD circuitreceives a CMD input from TMS on the falling edge of TCK. In response tothe CMD input, the CMD circuit outputs control to the routing circuit tocause the routing circuit to output DRC control on bus 2504 to perform acapture operation on the rising edge of TCK at time point 2520.Following the capture operation the data register resumes shifting datafrom TDI to TDO on the rising edge of TCK at time point 2522.

It is important to the note in FIG. 25C that the CS data registercapture operation 2520 occurs on the next rising edge TCK after lastshift (Shift-N) operation 2516. This provides a capture timingimprovement over a conventional TSM controlled CS data register captureoperation which, as seen in FIG. 7 , occurs four TCKs after the lastshift (Shift-N) operation update operation. The disclosures ability toperform a capture operation one TCK after the last shift operationallows testing for circuit timing related problems that cannot be testedusing a conventional TSM controlled shift and capture operation.

As seen in the timing diagrams of FIGS. 25B and 25C the TMS signal inputoperation is modified to enable the new control approach of thedisclosure by inputting the normal TMS signal to the TSM 104 on therising edge of TCK then switching the TMS signal input to input either ano-operation (NOP) signal or the CMD signal to the CMD circuit 2404 onthe falling edge of TCK. In this example, the NOP signal input on TMS isa low logic state signal and the CMD signal input on TMS is a high logicstate signal. However it should be understood that the logic states ofthe NOP and CMD signals could be reversed if desired.

FIGS. 26A-26C are provided to indicate that the NOP and CMD signalscould be input via the TDI signal instead of the TMS signal. FIG. 26A isidentical to FIG. 25A with the exception that the NOP and CMD inputscome from TDI instead of TMS. Timing FIGS. 26B and 26C are identical totiming FIGS. 25B and 25C with the exception that TDI is used to inputthe NOP and CMD signals on the falling edge of TCK instead of using TMS.While TDI can be used to input the NOP and CMD signals, there is anadvantage of using TMS for inputting NOP and CMD signals. This advantagewill be described later in regard to FIGS. 57A, 58A, 62A, 63A and 64Aillustrating devices that are connected in a daisy-chain arrangement toa controller.

The advantage of using the TAP's TMS or TDI input to input the NOP andCMD signals is that no additional device input is required to inputcommands to the CMD circuit.

The CMD circuit 2404 of FIGS. 25A and 26A may be designed in manydifferent ways including but not limited to the example designs shown inregard to FIGS. 27A-27D.

FIG. 27A illustrates a CMD circuit 2404 design example comprising astate machine 2702. The state machine 2702 has inputs for receiving theTMS signal of FIG. 25A or the TDI signal of 26A, an inverted TCK signal,and the Shift signal. The state machine 2702 has outputs for outputtingcontrol signals, in this example the C1 and C2 control signals. When theShift signal from the TSM is asserted, the state machine responds to aCMD signal input on the TMS/TDI input on the falling edge of TCK tooutput C1 and C2 control to perform the described capture and shift orthe described capture, shift and update operations on the data register108 of FIGS. 25A and 26A. If the data register 108 is a CS dataregister, the state machine will be designed to output capture and shiftcontrol to the data register in response to the CMD input. If the dataregister 108 is a CSU data register, the state machine will be designedto output capture, and update control to the data register in responseto the CMD input.

FIG. 27B illustrates a CMD circuit 2404 design example comprising aprogrammable state machine 2704. The programmable state machine 2702 hasinputs for receiving the TMS signal of FIG. 25A or the TDI signal of26A, an inverted TCK signal, the Shift signal and DRE input from theinstruction register 106, shown in dotted line in FIGS. 25A and 26A. Theprogrammable state machine 2704 has outputs for outputting controlsignals, in this example the C1 and C2 control signals. When the Shiftsignal from the TSM is asserted, the programmable state machine respondsto a CMD signal input on the TMS/TDI input on the falling edge of TCK tooutput C1 and C2 control to perform an operation programmed by the DREinputs. The programmed operation could be; (1) controlling a CSU dataregister to perform a capture, shift and update operation as shown intiming diagram 25B, (2) controlling a CS data register to perform acapture and shift operation as shown in timing diagram 25C or (3)controlling other types operations to other types of data registers orsimilar circuits.

FIG. 27C illustrates a very simple CMD circuit 2404 design examplecomprising only two serially connected FFs 2706 and 2708. FF 2706 has adata input for receiving the TMS signal of FIG. 25A or the TDI signal of26A, a clock input for receiving an inverted TCK signal, a reset inputfor receiving the Shift signal, and a data output for outputting a C1control signal. FF 2708 has a data input for receiving input from thedata output from FF 2706, a clock input for receiving an inverted TCKsignal, a reset input for receiving the Shift signal, and a data outputfor outputting a C1 control signal. When the Shift signal from the TSMis asserted, the reset condition to the FFs 2706 and 2708 is removed andthe FFs start shifting data from the TMS/TDI input on the falling edgeof TCK. When a CMD signal is input to FF 2706 (a logic high in thisexample) from the TMS/TDI input the data output of FF 2706 will be sethigh on the falling edge of TCK, which sets the C1 control signal high.On the next falling edge of TCK the data output of FF 2708 will be sethigh by the high output from FF 2706, which sets the C2 control signalhigh. As seen in FIGS. 25B and 25C, the CMD signal is a temporary logichigh signal that is asserted prior to a first falling edge TCK to setthe C1 output of FF 2706 high and is de-asserted to a logic low signalprior to the next (second) falling edge TCK to set the C1 output backlow. As C1 is set low on the second falling edge TCK, C2 from FF 2708 isset high. On a third (next) falling edge TCK both C2 is set back low andC1 remains low. As can be seen, the CMD circuit 2404 example of FIG. 27Csimply operates to shift the temporary logic high CMD signal through FFs2706 and 2708 on the falling edge of TCK to temporarily set the C1control signal high then set the C2 control signal high.

When the CMD circuit 27C is coupled to a CSU data register, thetemporary C1 signal causes the data register to perform an updateoperation on the rising edge of TCK and the temporary C2 signal causesthe data register to perform a capture operation on the rising edge ofTCK. Following the temporary C1 and C2 signal operations the CSU dataregister performs rising edge shift operations. The update, capture andshift timing of the CSU data register is as shown in FIG. 25B. When theCMD circuit 27C is coupled to a CS data register, the temporary C1signal causes the data register to perform a capture operation on therising edge of TCK. Following the temporary C1 signal operation the CSdata register performs rising edge shift operations. The capture andshift timing of the CS data register is as shown in FIG. 25C.

FIG. 27D is provided simply illustrate how the very simple CMD circuit2404 design example of FIG. 27C can be expanded to include an additionalcontrol output signal C3 by simply adding a third FF 2710 to the serialoutput of the second FF 2708. The additional control output signal C3can be used to provide an additional control function in response to aCMD input to FF 2706. Further additional control functions, C4-Cn, canbe added simply by adding additional FFs to the serial path of FFs. Thestate machine CMD circuits 2404 of FIGS. 27A and 27B can similarly bedesigned to include additional control outputs if required.

FIG. 28 illustrates the previously described FIG. 9 asynchronous CSUdata register 902 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled, operates in one of two modes.The first mode allows the TSM to control scan access to the dataregister 902 as described in regard to FIGS. 9 and 11 . The second modeallows the CMD circuit 2404 within the commandable DRC router 2402 tocontrol scan access to the data register 902. The operation modes aredetermined by DRE inputs from the instruction register 106. A firstinstruction loaded into the instruction register enables the dataregister 902 to be controlled by the TSM and a second instruction loadedinto the instruction register enables the data register to be controlledby the CMD circuit 2404.

FIG. 29 illustrates the commandable DRC router 2402 of FIG. 28 whichcomprises a CMD circuit 2404 and a routing circuit 2902. The CMD circuit2404 could be, but not limited to, the simple CMD circuit of FIG. 27C,or the state machine controlled CMD circuits of FIGS. 27A and 27B. Therouting circuit comprises the gating circuits 1102, 1104, and 1106 ofFIG. 11 , multiplexers 2904 and 2906 and gating circuit 2908, allconnected as shown.

In response to the above mentioned first instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1102 and optional clock multiplexer 1108 (ifincluded), the ShiftDR output of the TSM to the ShiftDR input of thedata register via gating circuit 1104 and multiplexer 2904 and theUpdateDR output of the TSM to the UpdateDR input of the data registervia gating circuit 1106 and multiplexer 2906. As can be seen, the firstinstruction enables scan access to the data register from the TSM asdescribed in regard to the routing circuit 906 of FIG. 9 .

In response to the above mentioned second instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1102 and optional clock multiplexer 1108 (ifincluded), the C2 output of the CMD circuit 2404 to the ShiftDR input ofthe data register via gating circuit 1104 and multiplexer 2904 and theC1 output of the CMD circuit to the UpdateDR input of the data registervia gating circuit 1106, multiplexer 2906 and gating circuit 2908.

When the TSM enters the Shift-DR state of FIG. 2 TCKs are output on theClockDR signal and the C1 and C2 control outputs from the CMD circuitare set to cause the data register to shift data from TDI to TDO on therising edge of the ClockDR signals. Also during the Shift-DR state theShift input from TSM is asserted to enable the CMD circuit 2404 to inputa CMD from TMS in response to the TCK signal. In response to a CMDinput, CMD circuit 2404 sets C1 high on the falling edge of TCK toenable a rising edge TCK signal to be passed through gating circuit 2908to multiplexer 1106 and gating circuit 1106 to perform an updateoperation on data register 902. Next the CMD circuit 2404 sets C1 backlow and C2 high on the falling edge of TCK to control the ShiftDR signalinput to data register 902, via multiplexer 2904 and gating circuit1104, to perform a rising edge ClockDR capture operation on dataregister 902. Following the C1 controlled update operation and C2controlled capture operation, the CMD circuit 2404 sets C2 back low andmaintains a low on C1 to cause the data register 902 to resume shiftingdata on the rising edge of ClockDR from TDI to TDO. The update andcapture operations repeat, while the TSM is in the Shift-DR state ofFIG. 2 , each time a CMD is input to CMD circuit 2404. As can be seen,the second instruction enables the data register 902 to cycle throughthe uninterrupted update, capture and shift operations of FIG. 25B inresponse to the C1 and C2 control signals from CMD circuit 2404 and theClockDR signal from the TSM.

FIG. 30 illustrates the previously described FIG. 13 asynchronous CSdata register 1302 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled, operates in one of two modes.The first mode allows the TSM to control scan access to the dataregister 1302 as described in regard to FIGS. 13 and 15 . The secondmode allows the CMD circuit 2404 within the commandable DRC router 2402to control scan access to the data register 1302. The operation modesare determined by DRE inputs from the instruction register 106. A firstinstruction loaded into the instruction register enables the dataregister 1302 to be controlled by the TSM and a second instructionloaded into the instruction register enables the data register to becontrolled by the CMD circuit 2404.

FIG. 31 illustrates the commandable DRC router 2402 of FIG. 28 whichcomprises a CMD circuit 2404 and a routing circuit 3102. The CMD circuit2404 could be, but not limited to, the simple CMD circuit of FIG. 27C,or the state machine controlled CMD circuits of FIGS. 27A and 27B. Therouting circuit comprises the gating circuits 1502 and 1504 of FIG. 15and multiplexer 3104, all connected as shown.

In response to the above mentioned first instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1502 and optional clock multiplexer 1108 (ifincluded) and the ShiftDR output of the TSM to the ShiftDR input of thedata register via gating circuit 1104 and multiplexer 3104. As can beseen, the first instruction enables scan access to the data registerfrom the TSM as described in regard to the routing circuit 1306 of FIG.13 .

In response to the above mentioned second instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1102 and optional clock multiplexer 1108 (ifincluded) and the C1 output of the CMD circuit 2404 to the ShiftDR inputof the data register via gating circuit 1504 and multiplexer 3104.

When the TSM enters the Shift-DR state of FIG. 2 TCKs are output on theClockDR signal and the C1 control output from the CMD circuit is set tocause the data register to shift data from TDI to TDO on the rising edgeof the ClockDR signals. Also during the Shift-DR state the Shift inputfrom TSM is asserted to enable the CMD circuit 2404 to input a CMD fromTMS in response to the TCK signal. In response to a CMD input, CMDcircuit 2404 sets C1 high on the falling edge of TCK to control theShiftDR signal input to data register 1302, via multiplexer 3104 andgating circuit 1504, to perform a rising edge ClockDR capture operationon data register 1302. Following the C1 controlled capture operation,the CMD circuit 2404 sets C1 back low to cause the data register 1302 toresume shifting data on the rising edge of ClockDR from TDI to TDO. Thiscapture operation repeats, while the TSM is in the Shift-DR state ofFIG. 2 , each time a CMD is input to CMD circuit 2404. As can be seen,the second instruction enables the data register 1302 to cycle throughthe uninterrupted capture and shift operations of FIG. 25C in responseto the C1 control signal from CMD circuit 2404 and the ClockDR signalfrom the TSM.

FIG. 32 illustrates the previously described FIG. 16 synchronous CSUdata register 1602 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled, operates in one of two modes.The first mode allows the TSM to control scan access to the dataregister 1602 as described in regard to FIGS. 16 and 18 . The secondmode allows the CMD circuit 2404 within the commandable DRC router 2402to control scan access to the data register 1602. The operation modesare determined by DRE inputs from the instruction register 106. A firstinstruction loaded into the instruction register enables the dataregister 1602 to be controlled by the TSM and a second instructionloaded into the instruction register enables the data register to becontrolled by the CMD circuit 2404.

FIG. 33 illustrates the commandable DRC router 2402 of FIG. 32 whichcomprises a CMD circuit 2404 and a routing circuit 3302. The CMD circuit2404 could be, but not limited to, the simple CMD circuit of FIG. 27C,or the state machine controlled CMD circuits of FIGS. 27A and 27B. Therouting circuit comprises the gating circuits 1802, 1804, and 1806 ofFIG. 18 and multiplexers 3304, 3306 and 3308 and gating circuit 3310,all connected as shown.

In response to the above mentioned first instruction, DRE inputs couplethe Capture output from the TSM to the Capture input of the dataregister via gating circuit 1802 and multiplexer 3304, the Shift outputof the TSM to the Shift input of the data register via gating circuit1804 and multiplexer 3306 and the Update output of the TSM to the Updateinput of the data register via gating circuit 1806 and multiplexer 3308.As can be seen, the first instruction enables scan access to the dataregister from the TSM as described in regard to the routing circuit 1606of FIG. 16 .

In response to the above mentioned second instruction, DRE inputs couplethe C2 output of CMD circuit 2404 to the Capture input of the dataregister via gating circuit 1802 and multiplexer 3304, the C2 output ofCMD circuit 2404 to the Shift input of the data register via gatingcircuit 1804, multiplexer 3306 and gating circuit 3310, the C1 output ofthe CMD circuit to the Update input of the data register via gatingcircuit 1806 and multiplexer 3308 and the C1 output of the CMD circuitto the Shift input of the data register via gating circuit 3310,multiplexer 3306 and gating circuit 1804.

When the TSM enters the Shift-DR state of FIG. 2 the C1 and C2 controloutputs from the CMD circuit are set to cause the data register to shiftdata from TDI to TDO on the rising edge of the TCK signal. Also duringthe Shift-DR state the Shift input from TSM is set to enable the CMDcircuit 2404 to input a CMD from TMS in response to the TCK signal. Inresponse to a CMD input, CMD circuit 2404 asserts a control signal on C1on the falling edge of TCK. The C1 control signal passes through gatingcircuit 3310, multiplexer 3306 and gating circuit 1804 to set the Shiftinput to the data register to a non-shifting state. The C1 controlsignal also passes through multiplexer 3308 and gating circuit 1806 toset the Update signal of the data register to the update state. With theUpdate signal set to the update state, the data register performs anupdate operation on the next rising edge of the TCK signal.

Next the CMD circuit 2404 de-asserts the C1 control signal and asserts acontrol signal on C2 on the falling edge of TCK. The C2 control signalpasses through multiplexer 3304 and gating circuit 1802 to set theCapture input to the data register to the capture state. The C2 controlsignal also passes through gating circuit 3310, multiplexer 3306 andgating circuit 1804 to maintain the non-shifting state on the Shiftinput to the data register. With the Capture signal set to the capturestate, the data register performs a capture operation on the next risingedge of the TCK signal.

Next the CMD circuit 2404 de-asserts C1 and C2 on the falling edge ofTCK which sets the Shift signal back to the shifting state, the Updatesignal to a non-update state and the Capture signal to a non-capturestate. With the Shift signal set to the shifting state, the dataregister resumes shifting data from TDI to TDO on the next rising edgeof the TCK signal. The update and capture operations repeat, while theTSM is in the Shift-DR state of FIG. 2 , each time a CMD is input to CMDcircuit 2404. As can be seen, the second instruction enables the dataregister 1602 to cycle through the uninterrupted update, capture andshift operations of FIG. 25B in response to the C1 and C2 controlsignals from CMD circuit 2404 and the TCK signal input. As seen in FIG.32 , the optional clock multiplexer 1608 may be included in the TCKsignal path.

FIG. 34 illustrates the previously described FIG. 19 synchronous CS dataregister 1902 coupled to TSM 104 via a commandable DRC router 2402. Thecommandable DRC router, when enabled, operates in one of two modes. Thefirst mode allows the TSM to control scan access to the data register1902 as described in regard to FIGS. 19 and 21 . The second mode allowsthe CMD circuit 2404 within the commandable DRC router 2402 to controlscan access to the data register 1902. The operation modes aredetermined by DRE inputs from the instruction register 106. A firstinstruction loaded into the instruction register enables the dataregister 1902 to be controlled by the TSM and a second instructionloaded into the instruction register enables the data register to becontrolled by the CMD circuit 2404.

FIG. 35 illustrates the commandable DRC router 2402 of FIG. 34 whichcomprises a CMD circuit 2404 and a routing circuit 3502. The CMD circuit2404 could be, but not limited to, the simple CMD circuit of FIG. 27C,or the state machine controlled CMD circuits of FIGS. 27A and 27B. Therouting circuit comprises the gating circuits 2102 and 2104 of FIG. 21and multiplexers 3504 and 3506, all connected as shown.

In response to the above mentioned first instruction, DRE inputs couplethe Capture output from the TSM to the Capture input of the dataregister via gating circuit 2102 and multiplexer 3504 and the Shiftoutput of the TSM to the Shift input of the data register via gatingcircuit 2104 and multiplexer 3506. As can be seen, the first instructionenables scan access to the data register from the TSM as described inregard to the routing circuit 1906 of FIG. 19 .

In response to the above mentioned second instruction, DRE inputs couplethe C1 output of CMD circuit 2404 to the Capture input of the dataregister via gating circuit 2102 and multiplexer 3504 and to the Shiftinput of the data register via gating circuit 2104 and multiplexer 3506.

When the TSM enters the Shift-DR state of FIG. 2 the C1 control outputfrom the CMD circuit is set to cause the data register to shift datafrom TDI to TDO on the rising edge of the TCK signal. Also during theShift-DR state the Shift input from TSM is set to enable the CMD circuit2404 to input a CMD from TMS in response to the TCK signal. In responseto a CMD input, CMD circuit 2404 asserts a control signal on C1 on thefalling edge of TCK. The C1 control signal passes through multiplexer3506 and gating circuit 2104 to set the Shift input to the data registerto a non-shifting state. The C1 control signal also passes throughmultiplexer 3504 and gating circuit 2102 to set the Capture signal ofthe data register to the capture state. With the Capture signal set tothe capture state, the data register performs a capture operation on thenext rising edge of the TCK signal.

Next the CMD circuit 2404 de-asserts the C1 control signal on thefalling edge of TCK which sets the Shift signal back to the shiftingstate and the Capture signal to a non-capture state. With the Shiftsignal set to the shifting state, the data register resumes shiftingdata from TDI to TDO on the next rising edge of the TCK signal. Thiscapture operation repeats, while the TSM is in the Shift-DR state ofFIG. 2 , each time a CMD is input to CMD circuit 2404. As can be seen,the second instruction enables the data register 1902 to cycle throughthe uninterrupted capture and shift operations of FIG. 25C in responseto the C1 control signal from CMD circuit 2404 and the TCK signal input.As seen in FIG. 34 , the optional clock multiplexer 1608 may be includedin the TCK signal path.

FIG. 36 illustrates the example test compression architecture (TCA) 2202of FIG. 22 within a device coupled to a TSM 104 via the commandable DRCrouter 2402 described in FIGS. 30 and 31 .

When commandable DRC router 2402 is enabled by DRE inputs of a firstinstruction loaded into the instruction register, the commandable DRCrouter 2402 couples the ClockDR and ShiftDR outputs of TSM 104 to theClockDR and ShiftDR inputs to the TCA 2202. In response to the firstinstruction, the TCA operates in response to the TSM ClockDR and ShiftDRsignals as described in regard to FIG. 22 .

When commandable DRC router 2402 is enabled by DRE inputs of a secondinstruction loaded into the instruction register, the commandable DRCrouter 2402 couples the ClockDR output of TSM 104 to the ClockDR inputof T2202 and couples the C1 output of CMD circuit 2404 to the ShiftDRinput of the TCA.

When the TSM enters the Shift-DR state of FIG. 2 , TCKs are output onthe ClockDR signal and the C1 control output from the CMD circuit is setto cause the TCA to shift compressed test data into TDI and compressedtest data from TDO on the rising edge of the ClockDR signals. Alsoduring the Shift-DR state the Shift input from TSM is asserted to enablethe CMD circuit 2404 to input a CMD from TMS in response to the TCKsignal. In response to a CMD input, CMD circuit 2404 asserts C1 on thefalling edge of TCK to control the ShiftDR signal input to TCA 2202, viamultiplexer 3104 and gating circuit 1504, to cause scan paths 2206 toperform a capture operation on the rising edge of ClockDR. Also while C1is asserted, the ShiftDR signal initializes the decompressor circuit2204 to receive compressed test data input from TDI. Following the C1controlled capture and initialization operations, the CMD circuit 2404de-asserts C1 which sets the ShiftDR signal to cause the decompressor toinput compressed test data from TDI and the scan paths 2206 to shiftdata from TDI to TDO via decompressor circuit 2204 and compactor circuit2208 on the rising edge of ClockDR. This capture and initializationoperation repeats, while the TSM is in the Shift-DR state of FIG. 2 ,each time a CMD is input to CMD circuit 2404. As can be seen, the secondinstruction enables the TCA 2202 to cycle through the uninterruptedcapture (and initialization) and shift operations of FIG. 25C inresponse to the C1 control signal from CMD circuit 2404 and the ClockDRsignal from the TSM.

As seen in FIG. 36 , clock multiplexer 1108 shown and described inregard to FIGS. 11 and 12 can be included in the ClockDR path to thescan cells of the scan paths 2206 to allow the scan cells to be drivenby either the ClockDR signal during test mode or by a FC during non-testmode.

FIG. 37 illustrates the example test compression architecture (TCA) 2302of FIG. 23 within a device coupled to a TSM 104 via the commandable DRCrouter 2402 described in FIGS. 34 and 35 .

When commandable DRC router 2402 is enabled by DRE inputs of a firstinstruction loaded into the instruction register, the commandable DRCrouter 2402 couples the Capture and Shift outputs of TSM 104 to theCapture and Shift inputs to TCA 2302. In response to the firstinstruction, the TCA operates in response TCK and the Capture and Shiftinput signals as described in regard to FIG. 23 .

When commandable DRC router 2402 is enabled by DRE inputs of a secondinstruction loaded into the instruction register, the commandable DRCrouter 2402 couples the C1 output of CMD circuit 2404 to the Captureinput of TCA 2303 via multiplexer 3504 and gating circuit 2102 and tothe Shift input of TCA 2302 via multiplexer 3506 and gating circuit2104.

When the TSM enters the Shift-DR state of FIG. 2 , the C1 control outputfrom CMD circuit 2404 is set to cause TCA 2302 to shift in compressedtest data from TDI and shift out compressed test data from TDO inresponse to the rising edge of the free running TCK signal. Also duringthe Shift-DR state the Shift input from TSM is asserted to enable theCMD circuit 2404 to input a CMD from TMS in response to the TCK signal.In response to a CMD input, CMD circuit 2404 asserts C1 on the fallingedge of TCK to control the Capture input to TCA 2302, via multiplexer3504 and gating circuit 2102, and the Shift input to TCA 2302, viamultiplexer 3506 and gating circuit 2104, to cause the scan paths 2306to perform a capture operation on the rising edge of TCK. Also while C1is asserted, the Capture signal or the Capture and Shift signalsinitialize the decompressor circuit 2304 to receive compressed test datainput from TDI. Following the C1 controlled capture and initializationoperations, the CMD circuit 2404 de-asserts C1 which sets the Captureand Shift signals to cause the decompressor to input compressed testdata from TDI and the scan paths 2306 to shift data from TDI to TDO viadecompressor circuit 2304 and compactor circuit 2308 on the rising edgeof TCK. This capture and initialization operation repeats, while the TSMis in the Shift-DR state of FIG. 2 , each time a CMD is input to CMDcircuit 2404. As can be seen, the second instruction enables the TCA2302 to cycle through the uninterrupted capture (and initialization) andshift operations of FIG. 25C in response to the C1 control signal fromCMD circuit 2404 and the TCK signal.

As seen in FIG. 37 , clock multiplexer 1608 shown and described inregard to FIGS. 16 and 19 can be included in the TCK path to the scancells of scan paths 2306 to allow the scan cells to be driven by eitherthe TCK signal during test mode or by a FC during non-test mode.

While the above descriptions of FIGS. 24-37 have described commandableDRC routers 2402 that use a first instruction to enable conventionalaccess to data registers and TCAs using the TSM and a second instructionto enable commanded access to data registers and TCAs using the CMDcircuit, commandable DRC routers 2402 are not limited to providing bothTSM and CMD circuit access to data registers and TCAs. According to thedisclosure and described below, commandable DRC routers 2402 may berealized that only use the second instruction to enable the CMD circuitfor commanded access to data registers and TCAs.

FIG. 38 illustrates the previously described FIG. 9 asynchronous CSUdata register 902 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled by DRE inputs of the secondinstruction mentioned in regard to FIGS. 28 and 29 , allows the CMDcircuit 2404 within the commandable DRC router 2402 to control scanaccess to the data register 902.

FIG. 39 illustrates the commandable DRC router 2402 of FIG. 38 whichcomprises a CMD circuit 2404 and a routing circuit 3902. The CMD circuit2404 could be, but not limited to, any of the CMD circuits of FIGS.27A-27C. The routing circuit 3902 of FIG. 39 is similar to the routingcircuit 2902 of FIG. 29 with the exception that it does not includemultiplexers 2904 and 2906 to provide TSM control of the ShiftDR andUpdateDR signal inputs to data register 902. As seen the routing circuit3902 comprises gating circuits 1102, 1104, 1106 and 2908 of FIG. 29 ,all connected as shown.

In response to the above mentioned second instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1102 and optional clock multiplexer 1108 (ifincluded), the C2 output of the CMD circuit 2404 to the ShiftDR input ofthe data register via gating circuit 1104 and the C1 output of the CMDcircuit to the UpdateDR input of the data register via gating circuits1106 and 2908.

When the TSM enters the Shift-DR state of FIG. 2 TCKs are output on theTSM ClockDR signal and the C1 and C2 control outputs from the CMDcircuit are set to cause the data register to shift data from TDI to TDOon the rising edge of the ClockDR signals. Also during the Shift-DRstate the Shift input from TSM is asserted to enable the CMD circuit2404 to input a CMD from TMS in response to the TCK signal. In responseto a CMD input, CMD circuit 2404 operates the C1 and C2 signals tocontrol the UpdateDR and ShiftDR data register inputs to cause the dataregister 902 to perform update and capture operations as described bythe second instruction of FIGS. 28 and 29 . The update and captureoperations repeat, while the TSM is in the Shift-DR state of FIG. 2 ,each time a CMD is input to CMD circuit 2404. As can be seen, the secondinstruction enables the data register 902 to cycle through theuninterrupted update, capture and shift operations of FIG. 25B inresponse to the C1 and C2 control signals from CMD circuit 2404 and theClockDR signal from the TSM.

FIG. 40 illustrates the previously described FIG. 13 asynchronous CSdata register 1302 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled by DRE inputs of the secondinstruction mentioned in regard to FIGS. 30 and 31 , allows the CMDcircuit 2404 within the commandable DRC router 2402 to control scanaccess to the data register 1302.

FIG. 41 illustrates the commandable DRC router 2402 of FIG. 40 whichcomprises a CMD circuit 2404 and a routing circuit 4102. The CMD circuit2404 could be, but not limited to, any of the CMD circuits of FIGS.27A-27C. The routing circuit 4102 of FIG. 41 is similar to the routingcircuit 3102 of FIG. 31 with the exception that it does not includemultiplexer 3104 to provide TSM control of the ShiftDR signal input todata register 1302. As seen the routing circuit 4102 comprises gatingcircuits 1502 and 1504 of FIG. 31 , all connected as shown.

In response to the above mentioned second instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the dataregister via gating circuit 1502 and optional clock multiplexer 1108 (ifincluded) and the C1 output of the CMD circuit 2404 to the ShiftDR inputof the data register via gating circuit 1504.

When the TSM enters the Shift-DR state of FIG. 2 , TCKs signals areoutput on the TSM ClockDR signal and the C1 control output from the CMDcircuit is set to cause the data register to shift data from TDI to TDOon the rising edge of the ClockDR signals. Also during the Shift-DRstate the Shift input from TSM is asserted to enable the CMD circuit2404 to input a CMD from TMS in response to the TCK signal. In responseto a CMD input, CMD circuit 2404 operates the C1 signal to control theShiftDR data register input to cause the data register 1302 to perform acapture operation as described by the second instruction of FIGS. 30 and31 . The capture operation repeats, while the TSM is in the Shift-DRstate of FIG. 2 , each time a CMD is input to CMD circuit 2404. As canbe seen, the second instruction enables the data register 1302 to cyclethrough the uninterrupted capture and shift operations of FIG. 25 c inresponse to the C1 control signal from CMD circuit 2404 and the ClockDRsignal from the TSM.

FIG. 42 illustrates the previously described FIG. 16 synchronous CSUdata register 1602 coupled to TSM 104 via a commandable DRC router 2402.The commandable DRC router, when enabled by DRE inputs of the secondinstruction mentioned in regard to FIGS. 32 and 33 , allows the CMDcircuit 2404 within the commandable DRC router 2402 to control scanaccess to the data register 1602.

FIG. 43 illustrates the commandable DRC router 2402 of FIG. 42 whichcomprises a CMD circuit 2404 and a routing circuit 4302. The CMD circuit2404 could be, but not limited to, any of the CMD circuits of FIGS.27A-27C. The routing circuit 4302 of FIG. 43 is similar to the routingcircuit 3302 of FIG. 33 with the exception that it does not includemultiplexers 3304, 3306 and 3308 to provide TSM control of the Capture,Shift and Update signal inputs to data register 1602. As seen therouting circuit 4302 comprises gating circuits 1802, 1804, 1806 and 3310of FIG. 33 , all connected as shown.

In response to the above mentioned second instruction, DRE inputs couplethe C2 output from the CMD circuit to the Capture input of the dataregister via gating circuit 1802 and to the Shift input of the dataregister via gating circuits 3310 and 1804. The DRE inputs also couplethe C1 output of the CMD circuit to the Shift input of the data registervia gating circuits 3310 and 1804 and to the Update input of the dataregister via gating circuit 1806.

When the TSM enters the Shift-DR state of FIG. 2 the C1 and C2 controloutputs from the CMD circuit are set to cause the data register to shiftdata from TDI to TDO on the rising edge of the TCK signal. Also duringthe Shift-DR state the Shift input from TSM is asserted to enable theCMD circuit 2404 to input a CMD from TMS in response to the TCK signal.In response to a CMD input, CMD circuit 2404 operates the C1 and C2signals to control the Capture, Shift and Update data register inputs tocause the data register 1602 to perform update and capture operations asdescribed by the second instruction of FIGS. 32 and 33 . The update andcapture operations repeat, while the TSM is in the Shift-DR state ofFIG. 2 , each time a CMD is input to CMD circuit 2404. As can be seen,the second instruction enables the data register 1902 to cycle throughthe uninterrupted update, capture and shift operations of FIG. 25B inresponse to the C1 and C2 control signals from CMD circuit 2404 on therising edge of the TCK signal. As seen in FIG. 42 , the optional clockmultiplexer 1608 may be included in the TCK signal path.

FIG. 44 illustrates the previously described FIG. 19 synchronous CS dataregister 1902 coupled to TSM 104 via a commandable DRC router 2402. Thecommandable DRC router, when enabled by DRE inputs of the secondinstruction mentioned in regard to FIGS. 34 and 35 , allows the CMDcircuit 2404 within the commandable DRC router 2402 to control scanaccess to the data register 1902.

FIG. 45 illustrates the commandable DRC router 2402 of FIG. 44 whichcomprises a CMD circuit 2404 and a routing circuit 4502. The CMD circuit2404 could be, but not limited to, any of the CMD circuits of FIGS.27A-27C. The routing circuit 4502 of FIG. 45 is similar to the routingcircuit 3502 of FIG. 35 with the exception that it does not includemultiplexers 3504 and 3506 to provide TSM control of the Capture andShift signal inputs to data register 1902. As seen the routing circuit4402 comprises gating circuits 2102 and 2104 of FIG. 35 , all connectedas shown.

In response to the above mentioned second instruction, DRE inputs couplethe C1 output from the CMD circuit to the Capture input of the dataregister via gating circuit 2102 and to the Shift input of the dataregister via gating circuit 2104. When the TSM enters the Shift-DR stateof FIG. 2 the C1 control output from the CMD circuit is set to cause thedata register to shift data from TDI to TDO on the rising edge of theTCK signal. Also during the Shift-DR state the Shift input from TSM isasserted to enable the CMD circuit 2404 to input a CMD from TMS inresponse to the TCK signal. In response to a CMD input, CMD circuit 2404operates the C1 control signal to control the Capture and Shift dataregister inputs to cause the data register 1902 to perform capture andshift operations as described by the second instruction of FIGS. 34 and35 . The capture operation repeats, while the TSM is in the Shift-DRstate of FIG. 2 , each time a CMD is input to CMD circuit 2404. As canbe seen, the second instruction enables the data register 1902 to cyclethrough the uninterrupted capture and shift operations of FIG. 25C inresponse to the C1 control signal from CMD circuit 2404 on the risingedge of the TCK signal. As seen in FIG. 44 , the optional clockmultiplexer 1608 may be included in the TCK signal path.

FIG. 46 illustrates the CS data register 1302 of FIG. 13 coupled to TSM104 via a commandable DRC router 2402. The only difference between thedata register 1302 of FIG. 13 and data register 1302 of FIG. 46 is thatthe scan cells 1304, re-shown in FIG. 47 for convenience, are coupled tothe free running TCK signal instead of the gated ClockDR signal of FIG.13 . The commandable DRC router, when enabled by DRE inputs of aninstruction allows the CMD circuit 2404 within the commandable DRCrouter 2402 to control scan access to the data register 1302.

FIG. 48 illustrates the commandable DRC router 2402 of FIG. 46 whichcomprises a CMD circuit 2404 and a routing circuit 4802. The CMD circuit2404 could be, but not limited too, any of the CMD circuits of FIGS.27A-27C. The routing circuit 4802 of FIG. 48 comprises gating circuit4804, which simply couples, in response to DRE input, the C1 controloutput from CMD circuit 2404 to the Shift input of data register 1302.

In response to the above mentioned instruction, DRE inputs couple the C1output from the CMD circuit to the Shift input of the data register viagating circuit 4804. When the TSM enters the Shift-DR state of FIG. 2the C1 control output from the CMD circuit is set to cause the dataregister to shift data from TDI to TDO on the rising edge of the TCKsignal. Also during the Shift-DR state the Shift input from TSM isasserted to enable the CMD circuit 2404 to input a CMD from TMS inresponse to the TCK signal. In response to a CMD input, CMD circuit 2404operates the C1 control signal to control the Shift input to the dataregister to cause the data register to perform a capture operation thensets the C1 control signal to cause the data register to resume theshift operation. The capture operation repeats, while the TSM is in theShift-DR state of FIG. 2 , each time a CMD is input to CMD circuit 2404.As can be seen, the instruction enables the data register 1302 to cyclethrough the uninterrupted capture and shift operations of FIG. 25C inresponse to the C1 control signal from CMD circuit 2404 on the risingedge of the TCK signal. As seen in FIG. 46 , the optional clockmultiplexer 1608 may be included in the TCK signal path.

FIG. 49 illustrates the TCA 2202 of FIG. 36 coupled to TSM 104 via thecommandable DRC router 2402 of FIG. 41 . The commandable DRC router,when enabled by DRE inputs of the second instruction mentioned in regardto FIG. 36 , allows the CMD circuit 2404 within the commandable DRCrouter 2402 to control scan access to the TCA 2202.

In response to the above mentioned second instruction, DRE inputs couplethe ClockDR output from the TSM to the ClockDR input of the TCA viagating circuit 1502 and optional clock multiplexer 1108 (if included)and the C1 output of the CMD circuit 2404 to the ShiftDR input of theTCA via gating circuit 1504.

When the TSM enters the Shift-DR state of FIG. 2 , TCKs signals areoutput on the TSM ClockDR signal and the C1 control output from the CMDcircuit is set to cause the TCA to shift data from TDI to TDO on therising edge of the ClockDR signals. Also during the Shift-DR state theShift input from TSM is asserted to enable the CMD circuit 2404 to inputa CMD from TMS in response to the TCK signal. In response to a CMDinput, CMD circuit 2404 operates the C1 signal to control the ShiftDRinput to cause the TCA to perform capture and initialization operationsas described by the second instruction of FIG. 36 . The capture andinitialization operations repeat, while the TSM is in the Shift-DR stateof FIG. 2 , each time a CMD is input to CMD circuit 2404. As can beseen, the second instruction enables the TCA to cycle through theuninterrupted capture/initialize and shift operations of FIG. 25 c inresponse to the C1 control signal from CMD circuit 2404 and the ClockDRsignal from the TSM.

FIG. 50 illustrates the TCA 2302 of FIG. 37 coupled to TSM 104 via thecommandable DRC router 2402 of FIG. 45 . The commandable DRC router,when enabled by DRE inputs of the second instruction mentioned in regardto FIG. 37 , allows the CMD circuit 2404 within the commandable DRCrouter 2402 to control scan access to the TCA 2302.

In response to the above mentioned second instruction, DRE inputs couplethe C1 output from the CMD circuit 2404 to the Capture input of the TCAvia gating circuit 2102 and to the Shift input of the TCA via gatingcircuit 2104.

When the TSM enters the Shift-DR state of FIG. 2 , the C1 control outputfrom the CMD circuit is set to cause the TCA to shift data from TDI toTDO on the rising edge of the TCK signal. Also during the Shift-DR statethe Shift input from TSM is asserted to enable the CMD circuit 2404 toinput a CMD from TMS in response to the TCK signal. In response to a CMDinput, CMD circuit 2404 operates the C1 signal to control the Captureand Shift inputs to cause the TCA to perform a capture andinitialization operation as described by the second instruction of FIG.37 . The capture and initialization operation repeats, while the TSM isin the Shift-DR state of FIG. 2 , each time a CMD is input to CMDcircuit 2404. As can be seen, the second instruction enables the TCA tocycle through the uninterrupted capture/initialize and shift operationsof FIG. 25 c in response to the C1 control signal from CMD circuit 2404and the TCK signal.

FIG. 51 illustrates a TCA 5102 comprising the decompressor circuit 2304of FIG. 50 , the compactor circuit 2308 of FIG. 50 and a parallel groupof scan paths 1302 of FIG. 46 all connected as shown. The scan paths1302 comprise scan cells 1304 as shown in FIG. 47 . The TCA 5102 iscoupled to TSM 104 via the commandable DRC router 2402 of FIG. 48 . Thecommandable DRC router, when enabled by DRE inputs from an instruction,allows the CMD circuit 2404 within the commandable DRC router 2402 tocontrol scan access to the TCA 5102. In response to the instruction, DREinputs couple the C1 output from the CMD circuit 2404 to the Shift inputof the TCA via gating circuit 4804.

When the TSM enters the Shift-DR state of FIG. 2 , the C1 control outputfrom the CMD circuit is set to cause the TCA to shift data from TDI toTDO on the rising edge of the TCK signal. Also during the Shift-DR statethe Shift input from TSM is asserted to enable the CMD circuit 2404 toinput a CMD from TMS in response to the TCK signal. In response to a CMDinput, CMD circuit 2404 operates the C1 signal to control the Shiftinput causing the TCA to perform a capture and initialization operationas described by the second instruction of FIG. 37 . Following thecapture and initialization operation, C1 is set to cause the TCA toresume shifting data from TDI to TDO. The capture and initializationoperation repeats, while the TSM is in the Shift-DR state of FIG. 2 ,each time a CMD is input to CMD circuit 2404. As can be seen, theinstruction enables the TCA to cycle through the uninterruptedcapture/initialize and shift operations of FIG. 25 c in response to theC1 control signal from CMD circuit 2404 and the TCK signal. As seen, theTCA 5102 may include the clock multiplexer 1608 in the TCK path to thescan paths 1302.

While the TCA 5102 of FIG. 51 is shown being clocked by the TCK signal,it could be clocked by the ClockDR signal from the TSM as well byplacing a ClockDR gating circuit 1502 in the routing circuit 4802 of thecommandable DRC router 2402 of FIG. 48 .

FIG. 52 is provided to illustrate that both a commandable DRC router2402 and a conventional DRC router 110 may be used in a device tocontrol separate groups of data registers or TCAs 5202 and 5204. Inresponse to the DRE outputs of a first instruction the conventional DRCrouter 110 is enabled to allow the TSM 104 to control a selected dataregister or TCA of group 5204 as previously described. In response tothe DRE outputs of a second instruction the commandable DRC router 2402is enabled to allow the CMD circuit 2404 to control a selected dataregister or TCA of group 5202 as previously described.

FIG. 53A illustrates a controller 5302 coupled to a device 5304 forconventionally accessing a CSU type data register of the device (such asthe boundary scan register) using the TSM 104. As seen in timing diagramof FIG. 53B, the controller cycles the TSM through the states of FIG. 2to perform Capture, Shift and Update operations. As seen in FIG. 53B,the TSM controlled Update operation is delayed by one and one half TCKsafter the last Shift (Shift N) operation. Also as seen in FIG. 53B, theTSM controlled Capture operation is delayed by two and one half TCKsafter the Update operation. As mentioned earlier, delaying the Captureoperation by two and one half TCKs prevents being able to test fortiming sensitive circuit delay faults in a device. This is a well knownproblem of using the TSM to control CSU data registers.

FIG. 54A illustrates a controller 5402 coupled to a device 5404 foraccessing a CSU type data register of the device (such as the boundaryscan register) using the CMD circuit 2404 of the commandable DRC router2402 of the present disclosure. As seen in timing diagram of FIG. 54B,the controller transitions the TSM into the Shift-DR state of FIG. 2then inputs a CMD 5406 on TMS at an appropriate time to perform anUpdate and Capture operation then resumes the Shift operation. This CMDinput cycle repeats while the TSM is in the Shift-DR state. As seen inFIG. 54B, the CMD controlled Update operation occurs on the next TCKfollowing the last shift (Shift N) operation. Also as seen in FIG. 54B,the CMD controlled Capture operation occurs on the next TCK followingthe Update operation. Thus the CMD controlled method of the disclosureovercomes the testing limitation of the TSM control method of FIGS. 53Aand 53B and enables CSU data registers to test for timing sensitivecircuit delay faults in a device.

FIG. 55A illustrates a controller 5502 coupled to a device 5504 forconventionally accessing a CS type data register of the device (such asa scan path register) using the TSM 104. As seen in timing diagram ofFIG. 55B, the controller cycles the TSM through the states of FIG. 2 toperform Capture and Shift operations. As seen in FIG. 55B, the TSMcontrolled Capture operation is delayed by four TCKs after the lastShift (Shift-N) operation. Delaying the Capture operation by four TCKsprevents being able to test for timing sensitive circuit delay faults ina device. This is a well known problem of using the TSM to control CSdata registers.

FIG. 56A illustrates a controller 5602 coupled to a device 5604 foraccessing a CS type data register of the device (such as a scan pathregister) using the CMD circuit 2404 of the commandable DRC router 2402of the present disclosure. As seen in timing diagram of FIG. 56B, thecontroller transitions the TSM into the Shift-DR state of FIG. 2 theninputs a CMD 5606 on TMS at an appropriate time to perform a Captureoperation then resumes the Shift operation. This CMD input cycle repeatswhile the TSM is in the Shift-DR state. As seen in FIG. 56B, the CMDcontrolled Capture operation occurs on the next TCK following the lastshift (Shift N) operation. Thus the CMD controlled method of thedisclosure overcomes the testing limitation of the TSM control method ofFIGS. 55A and 55B and enables CS data registers to test for timingsensitive circuit delay faults in a device.

FIG. 57A illustrates a controller 5702 coupled to a daisy-chainarrangement of devices 5704-5708 for conventionally accessing theboundary scan registers of the devices to test the functionalinterconnects 5710 between the devices using TSM 104. As seen in timingdiagram of FIG. 57B, the controller cycles the TSM through the states ofFIG. 2 to perform Capture, Shift and Update operations. As seen in FIG.57B, the TSM controlled Update operation is delayed by one and one halfTCKs after the last Shift (Shift N) operation and the TSM controlledCapture operation is delayed by two and one half TCKs after the Updateoperation. Delaying the Capture operation by two and one half TCKs afterthe Update operation prevents being able to test for timing sensitivedelay faults in the interconnects 5710 between the devices. This is awell known problem of using the TSM to control device boundary scanregisters.

FIG. 58A illustrates a controller 5802 coupled to a daisy chainarrangement of devices 5804-5808 for accessing the boundary scanregisters of the devices to test the functional interconnects 5810between the devices using the CMD circuit 2404 of the commandable DRCrouter 2402 of the present disclosure. As seen in timing diagram of FIG.58B, the controller transitions the TSM into the Shift-DR state of FIG.2 then inputs a CMD 5812 on TMS at an appropriate time to perform anUpdate and Capture operation then resumes the Shift operation. This CMDinput cycle repeats while the TSM is in the Shift-DR state. As seen inFIG. 58B, the CMD controlled Update operation occurs on the next TCKfollowing the last shift (Shift N) operation and the CMD controlledCapture operation occurs on the next TCK following the Update operation.Thus the CMD controlled method of the disclosure overcomes the testinglimitation of the TSM control method of FIGS. 57A and 57B and enablestesting for timing sensitive delay faults in the interconnects 5810between the devices.

FIG. 59A illustrates a controller 5902 accessing a first device 5904 ina daisy-chain arrangement for conventionally accessing a data registeror TCA in the first device using the TSM while trailing devices5906-5908 are being bypassed (shown in dotted line) using the device'sTAP bypass register. If a CSU type data register is being accessed, theTSM will cycle through the previously described Capture, Shift andUpdate operations as shown in FIG. 59B. If a CS type data register isbeing accessed, the TSM will still cycle through the previouslydescribed Capture, Shift and Update operations as shown in FIG. 59C eventhough there is no update register. If a TCA is being accessed, the TSMwill still cycle through the previously described Capture, Shift andUpdate operations shown in FIG. 59C even though the TCA does requiredthe Update operation. As can be seen in both FIGS. 59B and 59C, the TSMcontrol method adds the previously described and undesired TCK delaysbetween the last Shift (Shift-N) operation and the Update operation andbetween the Update operation and the Capture operation. Further, eachShift operation needs to be extended with an additional number of shiftsto allow the data from the leading device 5904 to be output to thecontroller via the bypass registers of the trailing devices 5906-5908.The data must traverse the bypass registers during each Shift operationsince the bypass registers load with logic 0's during each Captureoperation. These are well known problems in using the TSM to controlaccess to a first device in a daisy-chain arrangement of devices.

FIG. 60A illustrates a controller 6002 accessing a middle device 6006 ina daisy-chain arrangement for conventionally accessing a data registeror TCA in the middle device using the TSM while leading devices 6004 andtrailing devices 6008 are being bypassed (shown in dotted line) usingthe device's TAP bypass register. If a CSU type data register is beingaccessed, the TSM will cycle through the previously described Capture,Shift and Update operations as shown in FIG. 60B. If a CS type dataregister is being accessed, the TSM will still cycle through thepreviously described Capture, Shift and Update operations as shown inFIG. 60C even though there is no update register. If a TCA is beingaccessed, the TSM will still cycle through the previously describedCapture, Shift and Update operations shown in FIG. 60C even though theTCA does required the Update operation. As can be seen in both FIGS. 60Band 60C, the TSM control method adds the previously described andundesired TCK delays between the last Shift (Shift-N) operation and theUpdate operation and between the Update operation and the Captureoperation. Further, each Shift operation needs to be extended with anadditional number of shifts to allow the input data to the middle device6006 to pass through the bypass registers of leading devices 6004 andthe output data from the middle device 6006 to pass through the bypassregisters of the trailing devices 6008. The data must traverse thebypass registers during each Shift operation since the bypass registersload with logic 0's during each Capture operation. These are well knownproblems in using the TSM to control access to a middle device in adaisy-chain arrangement of devices.

FIG. 61A illustrates a controller 6102 accessing a last device 6108 in adaisy-chain arrangement for conventionally accessing a data register orTCA in the last device using the TSM while leading devices 6104-6106 arebeing bypassed (shown in dotted line) using the device's TAP bypassregister. If a CSU type data register is being accessed, the TSM willcycle through the previously described Capture, Shift and Updateoperations as shown in FIG. 61B. If a CS type data register is beingaccessed, the TSM will still cycle through the previously describedCapture, Shift and Update operations as shown in FIG. 61C even thoughthere is no update register. If a TCA is being accessed, the TSM willstill cycle through the previously described Capture, Shift and Updateoperations shown in FIG. 61C even though the TCA does required theUpdate operation. As can be seen in both FIGS. 61B and 61C, the TSMcontrol method adds the previously described and undesired TCK delaysbetween the last Shift (Shift-N) operation and the Update operation andbetween the Update operation and the Capture operation. Further, eachShift operation needs to be extended with an additional number of shiftsto allow the input data to the last device 6108 to pass through thebypass registers of leading devices 6104-6106. The data must traversethe bypass registers during each Shift operation since the bypassregisters load with logic 0's during each Capture operation. These arewell known problems in using the TSM to control access to a last devicein a daisy-chain arrangement of devices.

FIG. 62A illustrates a controller 6202 accessing a data register or aTCA of a first device 6204 in a daisy-chain arrangement with trailingdevices 6206-6208 using the CMD method of the commandable DRC router2402 of the present disclosure. As seen in dotted line, the trailingdevices 6206-6208 in the arrangement are bypassed using their TAP bypassregister. If a CSU type data register is being accessed, the commandableDRC router 2404 will respond to a CMD input 6210 on TMS to cycle throughthe previously described Update, Capture and Shift operations as shownin FIG. 62B. If a CS type data register or a TCA is being accessed, thecommandable DRC router 2404 will respond to a CMD input 6212 on TMS tocycle through the previously described Capture and Shift operations asshown in FIG. 62C. As can be seen in both FIGS. 62B and 62C, the CMDcontrol method eliminates the undesired TCK delays mentioned in regardto the TSM control methods of FIGS. 59B and 59C.

Further, since the TSM 104 continuously shifts data in the Shift-DRstate during the CMD controlled method of the disclosure and onlysuspends the continuous shift operation to perform the commanded Captureor Update and Capture operations, the shift operation only needs to beextended by the number of trailing device bypass registers.

For example, if there are 10 trailing device bypass registers theoverall Shift operation will only be extended by 10 additional shiftoperations. In comparison, with 10 trailing device bypass registers inthe TSM control method of FIGS. 59 a -59C, each Shift cycle would needto be extended by 10 shifts. If 10,000 Shift cycles were required in theFIG. 59A-59C examples, the overall shift operation would be extended by10,000×10 shifts, or 100,000 additional shift operations.

FIG. 63A illustrates a controller 6302 accessing a data register or aTCA of a middle device 6306 in a daisy-chain arrangement with leadingdevices 6304 and trailing devices 6308 using the CMD method of thecommandable DRC router 2402 of the present disclosure. As seen in dottedline, the leading and trailing devices in the arrangement are bypassedusing their TAP bypass register. If a CSU type data register is beingaccessed, the commandable DRC router 2404 will respond to a CMD input6310 on TMS to cycle through the previously described Update, Captureand Shift operations as shown in FIG. 63B. If a CS type data register ora TCA is being accessed, the commandable DRC router 2404 will respond toa CMD input 6312 on TMS to cycle through the previously describedCapture and Shift operations as shown in FIG. 63C. As can be seen inboth FIGS. 63B and 63C, the CMD control method eliminates the undesiredTCK delays mentioned in regard to the TSM control methods of FIGS. 60Band 60C.

Further, since the TSM 104 continuously shifts data in the Shift-DRstate during the CMD controlled method of the disclosure and onlysuspends the continuous shift operation to perform the commanded Captureor Update and Capture operations, the shift operation only needs to beextended by the number of leading and trailing device bypass registers.

For example, if there are 5 leading and 5 trailing device bypassregisters the overall Shift operation will only be extended by 10additional shift operations. In comparison, with 5 leading and 5trailing device bypass registers in the TSM control method of FIGS. 60 a-60C, each Shift cycle would need to be extended by 10 shifts. If 10,000Shift cycles were required in the FIG. 60A-60C examples, the overallshift operation would be extended by 10,000×10 shifts, or 100,000additional shifts.

FIG. 64A illustrates a controller 6402 accessing a data register or aTCA of a last device 6408 in a daisy-chain arrangement with leadingdevices 6404-6406 using the CMD method of the commandable DRC router2402 of the present disclosure. As seen in dotted line, the leadingdevices 6404-6406 in the arrangement are bypassed using their TAP bypassregister. If a CSU type data register is being accessed, the commandableDRC router 2404 will respond to a CMD input 6410 on TMS to cycle throughthe previously described Update, Capture and Shift operations as shownin FIG. 64B. If a CS type data register or a TCA is being accessed, thecommandable DRC router 2404 will respond to a CMD input 6412 on TMS tocycle through the previously described Capture and Shift operations asshown in FIG. 64C. As can be seen in both FIGS. 64B and 64C, the CMDcontrol method eliminates the undesired TCK delays mentioned in regardto the TSM control methods of FIGS. 61B and 61C.

Further, since the TSM 104 continuously shifts data in the Shift-DRstate during the CMD controlled method of the disclosure and onlysuspends the continuous shift operation to perform the commanded Captureor Update and Capture operations, the shift operation only needs to beextended by the number of leading device bypass registers.

For example, if there are 10 leading device bypass registers the overallShift operation will only be extended by 10 additional shift operations.In comparison, with 10 leading device bypass registers in the TSMcontrol method of FIGS. 61 a -61C, each Shift cycle would need to beextended by 10 shifts. If 10,000 Shift cycles were required in the FIG.61A-61C examples, the overall shift operation would be extended by10,000×10 shifts, or 100,000 additional shift operations.

It is important to note in the daisy chain arrangements of FIGS. 62A-64Athe advantage of inputting the CMD signal to the commandable DRC routersusing the TMS signal, which is a common input to all the devices. Whileit was mentioned earlier in regard to FIGS. 26A-26C that the CMD signalcould be input using the TDI input, the TDI CMD input method would notwork when devices are placed in the daisy chain arrangements of FIGS.62A-64A since the TDI input from the controller is only connected to thefirst device in the daisy chain arrangement.

FIG. 65 illustrates the timing of a CS data register scan operationcontrolled from a commandable DRC router 2402 that performs two back toback Capture operations following the last Shift (Shift-N) operation.Performing back to back Capture operations are commonly done usingconventional scan interfaces, i.e. using scan clock and scan enablesignals, to provide improved circuit delay testing. In this case it isdone using the commandable DRC router of the present disclosure. As seenin FIG. 65 , a CMD 6502 is input to the commandable DRC router from TMSduring the last Shift operation. In response to the CMD input thecommandable DRC router outputs control to cause the data register toperform first and second Capture operations, then resumes the Shiftoperation.

FIG. 66 illustrates the CMD circuit 2404 of FIG. 27C that is modified toprovide control for back to back Capture operations. As seen themodifications include adding gating circuit 6602 and multiplexer 6604 tothe FIG. 27C circuit. When DRE control from a first instruction is inputto CMD circuit 2404 of FIG. 66 , multiplexer 6604 is controlled toselect the output of FF 2706 to be output on C1 and the CMD circuitoperates as the CMD circuit of FIG. 27C, i.e. it produces a single C1output in response to the CMD input. When DRE control from a secondinstruction is input to CMD circuit 2404 of FIG. 66 , multiplexer 6604is controlled to select the output of gating circuit 6602, which, inthis example, ORs the outputs of FFs 2706 and 2708. In response to a CMDinput while the second instruction is in effect, the CMD circuit of FIG.66 produces a first C1 output as the CMD input is shifted into FF 2706then a second C1 output as the CMD input is shifted into FF 2708. Thefirst C1 output performs the first Capture operation 6504 and the secondC1 output performs the second Capture operation 6506 of FIG. 65 . Thusthe CMD circuit of FIG. 66 can be programmed by the DRE input of thefirst instruction to perform a single Capture and Shift operation asseen in FIG. 25C and can be programmed by the DRE input of the secondinstruction to perform a back to back Capture and Shift operation asseen in FIG. 65 . For example, substituting the CMD circuit of FIG. 66for the CMD circuit of FIG. 41 would enable the commandable DR router2402 of FIG. 40 to operate the data register 1302 in a single captureand shift operation mode or in a back to back capture and shiftoperation mode.

FIG. 67A illustrates a device 6702 containing a conventional TAParchitecture connected in series with a device 6704 containing thecommanded TAP architecture of the present disclosure. When both devicesare loaded with instructions to enable the DRC Router (DR) 110 of device6702 and the Commandable DRC Router (CDR) 2402 of device 6704, tocontrol a data register or a TCA using DRC control from TSM 104, the TCKand TMS timing operates as shown in FIG. 67B. As seen in FIG. 67B, theTMS signal input is stable during the rising edge of TCK to inputcontrol to operate the TSM through the states of FIG. 2 . In thisexample, the CDR 2402 operates the same as DR 110 to perform thepreviously described conventional TSM controlled capture and shift orcapture, shift and update operations.

FIG. 68A illustrates the FIG. 67A devices 6702 and 6704 connected inseries. In this example, device 6702 has been loaded with an instruction(Bypass Instruction) that selects the TAP's Bypass Register as the dataregister between TDI and TDO and device 6704 has been loaded with aninstruction the selects a data register of TCA between TDI and TDO. Theinstruction loaded into device 6704 also enables the CDR 2402 to operatein response to CMD inputs from TMS as previously described.

When the TSMs of both devices are transitioned to the Shift-DR state ofFIG. 2 , data is shifted through both devices from TDI of device 6702 toTDO of device 6704. As seen in FIG. 68B, the TMS signal input is stableduring the rising edge of the TCK to input control to operate the TSMthrough its states and the TMS signal is stable during the falling edgeof TCK to input a NOP or a CMD signal to the CDR 2402. In response tothe CMD signal, the CDR 2402 operates to perform capture and shift orcapture, shift and updates operations as previously described.

The purpose of FIGS. 67A, 67B, 68A and 68B is simply to show thatconventional devices 6702 that sample TMS on the rising edge of TCK tocontrol their TSM 104 can operate compatibly with devices 6704 of thisdisclosure that sample TMS on the rising edge of TCK to control theirTSM and sample TMS on the falling edge of TCK to control their CDR 2402.Thus, and advantageously, devices containing the commanded TAParchitecture of the disclosure can be used with devices containingconventional TAP architectures since the state of TMS on the fallingedge of TCK is ignored in conventional TAP architectures.

FIG. 69 illustrates a device 6902 comprising a TSM 104, a commandableDRC router (CDR) 2402, and parallel data registers 1-N 108 all connectedas shown. The parallel data registers 108 could be any of the dataregisters 108 previously described in regard to FIGS. 9, 13, 16 and 19 .In this example the parallel data registers are assumed to be scan pathsdata registers for testing combinational logic in the device 6902. Thedata registers are all controlled by the DRC output from the CDR 2402 asthe single data registers of FIGS. 28-34 and FIGS. 38-46 were previouslydescribed being controlled to perform capture and shift or update,capture and shift operations.

As seen, a device tester 6904 is connected to the device 6902 to providea separate TDI input to each data register and receive a separate TDOoutput from each data register. The tester also provides the TCK and TMSinputs to the device's TSM 104 and CDR 2402. If the CDR 2402 of FIG. 69is like the CDRs 2402 described in regard to FIGS. 28-34 , the dataregisters can be selectively controlled by the TSM 104 or by the CMDcircuit 2404. If the CDR 2402 of FIG. 69 is like the CDRs 2402 describedin regard to FIGS. 38-46 , the data registers can be controlled by theCMD circuit 2404. The reduced test time advantage of using shorterlength parallel data registers for testing combinational logic ratherthan using a single longer length data register is well known in theindustry.

FIG. 70 illustrates a device 7002 comprising a TSM 104, a commandableDRC router (CDR) 2402, and a TCA 7006. The TCA 7006 is the same as thepreviously described TCAs with the exception that TCA 7006 has N TDIinputs for inputting compressed test data from a tester 7004 and N TDOoutputs for outputting compressed test data to the tester 7004. Thedecompressor circuit (D) decompresses the test data from the TDI inputsand inputs the decompressed test data to a large number of shorterlength scan path data registers (1-M). The compactor circuit (C)compacts the test data from the scan path data registers (1-M) intocompressed test data outputs that are output on the TDO outputs. The Mscan path data registers are used to test combinational logic in device7002. The TCA 7006 of FIG. 70 is controlled by the DRC output from theCDR 2402 as the TCAs of FIGS. 36-37 and FIGS. 49-51 were previouslydescribed being controlled.

As seen, a device tester 7004 is connected to the device 7002 to providethe separate TDI 1-N inputs to the TCA 7006 and receive the separate TDO1-N outputs from the TCA 7006. The tester also provides the TCK and TMSinputs to the device's TSM 104 and CDR 2402. If the CDR 2402 of FIG. 70is like the CDRs 2402 described in regard to FIGS. 36-37 , the TCA 7006can be selectively controlled by the TSM 104 or by the CMD circuit 2404.If the CDR 2402 of FIG. 70 is like the CDRs 2402 described in regard toFIG. 49-51 , the TCA 7006 can be controlled by the CMD circuit 2404. Thereduced test time advantage of using TCAs 7006 with more that onecompressed test input (i.e. TDI 1-N) and more that one compressed testdata output (i.e. TDO 1-N) rather than using a TCA with a singlecompressed test data input (i.e. TDI) and single compressed test dataoutput (i.e. TDO) is well known in the industry.

FIG. 71A illustrates a device 7102 comprising a TSM 104, a commandableDRC router (CDR) 2402, and a data register or TCA all connected asshown. The data register or TCA of FIG. 71A could be any of thepreviously described data registers or TCAs. The CDR 2402 of FIG. 71Acould be any of the previously described CDRs 2402. The only differencebetween device 7102 and other previously described devices that containa TSM 104, a CDR 2402 and a data register/TCA is that the CDR 2402 ofdevice 7102 receives the CMD input from a CMD input signal 7104 to thedevice that is separate from the TMS input signal to the device. When aninstruction is input to the instruction register 106, the DRE inputsfrom the instruction register enable the CDR 2402 to respond to CMDinputs from the CMD input signal 7104.

FIG. 71B illustrates the timing of inputting a CMD to CDR 2402 using theCMD input signal 7104 to perform an uninterrupted update, capture andshift operation. As seen, the TSM 104 is in the Shift-DR state shiftingdata to and from a data register or TCA. At an appropriate time, andbefore the falling edge of TCK, a CMD 7106 is input on the CMD inputsignal 7104 to CDR 2402. In response the CMD input, the CDR 2402controls the data register or TCA as previously described to perform anupdate, capture and shift operation cycle. Additional CMD inputs causeadditional uninterrupted update, capture and shift operation cycles tooccur.

FIG. 71C illustrates the timing of inputting a CMD to CDR 2402 using theCMD input signal 7104 to perform an uninterrupted capture and shiftoperation. As seen, the TSM 104 is in the Shift-DR state shifting datato and from a data register or TCA. At an appropriate time, and beforethe falling edge of TCK, a CMD 7106 is input on the CMD input signal7104 to CDR 2402. In response the CMD input, the CDR 2402 controls thedata register or TCA as previously described to perform a capture andshift operation cycle. Additional CMD inputs cause additionaluninterrupted capture and shift operation cycles to occur.

FIG. 72A illustrates a device 7202 comprising a TSM 104, a commandableDRC router (CDR) 7204, and a data register or TCA all connected asshown. The data register or TCA of FIG. 71A could be any of thepreviously described data registers, such as 1302, or TCAs, such as2202, that operate in response to ClockDR and ShiftDR inputs. CDR 7204inputs a ClockDR signal from TSM 104, a CMD signal from the CMD inputsignal 7104 and DRE input from instruction register 106. CDR 7204outputs a ClockDR and ShiftDR signal to the data register/TCA. When aninstruction is input to the instruction register 106, the DRE inputsfrom the instruction register enable the CDR 7204 to respond to CMDinputs from the CMD input signal 7104 to perform data register/TCAcapture and shift operation cycles as shown in FIG. 73 .

FIG. 72B illustrates an example CDR 7204 which comprises gating circuits7206 and 7208. Gating circuit 7206 inputs the ClockDR signal from TSM104 and a DRE input from instruction register 106. Gating circuit 7206outputs a ClockDR signal to the data register/TCA. Gating circuit 7208inputs the CMD signal from CMD input and a DRE input from instructionregister 106. Gating circuit 7206 outputs a ShiftDR signal to the dataregister/TCA. As can be seen, CDR 7204 does not include the CMD circuit2404 of CDRs 2402. The reason a CMD circuit 2402 is not required isbecause the CMD is input directly from the CMD input signal 7104 from anexternal controller or tester. Thus the CMD signal can be asserted bythe external controller or tester to a desired stable state prior to therising edge of the ClockDR (gated TCK) signal from the TSM 104. The CMDcircuit 2404 was required in CDRs 2402 since the CMD was input on TMSand registered on the falling edge of TCK such that it was asserted to adesired stable state prior to the rising edge of TCK.

FIG. 73 illustrates the timing of inputting a CMD to CDR 7204 using theCMD input signal 7104 to perform uninterrupted capture and shiftoperation cycles. As seen, the TSM 104 is in the Shift-DR state shiftingdata to and from a data register or TCA. At an appropriate time, andprior to the rising edge of TCK, a controller or tester inputs a CMDsignal 7210 on the CMD input 7104 to CDR 7204. In response to the CMDinput, CDR 7204 sets the ShiftDR input to the data register or TCA to astate that causes the data register or TCA to perform a captureoperation in response to the rising edge of the TCK (ClockDR) input.Following the CMD input the data register or TCA resumes the shifting ofdata. Additional CMD 7210 inputs cause additional uninterrupted captureand shift operation cycles to occur.

FIG. 74A illustrates a device 7402 comprising a TSM 104, a commandableDRC router (CDR) 7404, and a data register or TCA all connected asshown. The data register or TCA of FIG. 74A could be any of thepreviously described data registers, such as 1302, or TCAs, such as5102, that operate in response to the free running TCK and Shift inputs.CDR 7404 inputs a CMD signal from the CMD input signal 7104 and DREinputs from the instruction register 106. CDR 7404 outputs a Shiftsignal to the data register/TCA. When an instruction is input to theinstruction register 106, the DRE inputs from the instruction registerenable the CDR 7404 to respond to CMD inputs from the CMD input signal7104 to perform data register/TCA capture and shift operation cycles asshown in FIG. 73 .

FIG. 74B illustrates an example CDR 7404 which comprises a gatingcircuit 7406. Gating circuit 7406 inputs the CMD signal 7104 and a DREinput from instruction register 106. Gating circuit 7406 outputs a Shiftsignal to the data register/TCA. As can be seen, CDR 7404 does notinclude the CMD circuit 2404 of CDRs 2402 for the same reasons mentionedin regard to CDR 7204 of FIG. 72B. A controller or tester asserts theCMD signal to a desired stable state prior to the rising edge of the TCKsignal which causes gating circuit 7406 to set the Shift input to dataregister or TCA to a state that causes the data register or TCA tocapture data on the rising edge of TCK.

FIG. 73 illustrates the timing of inputting a CMD to CDR 7404 using theCMD input signal 7104 to perform uninterrupted capture and shiftoperation cycles. As seen, the TSM 104 is in the Shift-DR state shiftingdata to and from a data register or TCA. At an appropriate time, andprior to the rising edge of TCK, a controller or tester inputs a CMDsignal 7210 on the CMD input 7104 to CDR 7404. In response to the CMDinput, CDR 7404 sets the Shift input to the data register or TCA to astate that causes the data register or TCA to perform a captureoperation in response to the rising edge of the TCK input. Following theCMD input the data register or TCA resumes the shifting of data.Additional CMD 7210 inputs cause additional uninterrupted capture andshift operation cycles to occur.

FIG. 75A illustrates a device 7502 comprising a TSM 104, a commandableDRC router (CDR) 7504, and a data register or TCA all connected asshown. The data register or TCA of FIG. 75A could be any of thepreviously described data registers, such as 1302, or TCAs, such as2202, that operate in response to ClockDR and ShiftDR inputs. CDR 7504inputs ClockDR and ShiftDR signals from TSM 104, a CMD signal from theCMD input signal 7104 and DRE input from instruction register 106. CDR7504 outputs a ClockDR and ShiftDR signal to the data register/TCA.

FIG. 75B illustrates an example CDR 7504 comprising gating circuits 7506and 7508 and multiplexer 7510 all connected as shown. When a firstinstruction is input to the instruction register 106, the DRE inputsfrom the instruction register enable the CDR 7504 to respond to theClockDR and ShiftDR inputs from TSM 104 to perform data register/TCAcapture and shift operation cycles as described in FIG. 31 . When asecond instruction is input to the instruction register 106, the DREinputs from the instruction register enable the CDR 7504 to respond toCMD inputs from the CMD input signal 7104 to perform data register/TCAcapture and shift operation cycles as described in FIG. 31 . The onlydifference between the CDR 7504 of FIG. 75B and CDR 2402 of FIG. 31 isthat the CMD circuit 2404 of FIG. 35 is not included in FIG. 76B.

FIG. 76A illustrates a device 7602 comprising a TSM 104, a commandableDRC router (CDR) 7604, and a data register or TCA all connected asshown. The data register or TCA of FIG. 75A could be any of thepreviously described data registers, such as 1902, or TCAs, such as2302, that operate in response to Capture and Shift inputs. CDR 7604inputs Capture and Shift signals from TSM 104, a CMD signal from the CMDinput signal 7104 and DRE input from instruction register 106. CDR 7604outputs a Capture and Shift signal to the data register/TCA.

FIG. 76B illustrates an example CDR 7604 comprising gating circuits 7606and 7608 and multiplexers 7610 and 7612 all connected as shown. When afirst instruction is input to the instruction register 106, the DREinputs from the instruction register enable the CDR 7604 to respond tothe Capture and Shift inputs from TSM 104 to perform data register/TCAcapture and shift operation cycles as described in FIG. 35 . When asecond instruction is input to the instruction register 106, the DREinputs from the instruction register enable the CDR 7604 to respond toCMD inputs from the CMD input signal 7104 to perform data register/TCAcapture and shift operation cycles as described in FIG. 35 . The onlydifference between the CDR 7604 of FIG. 76B and CDR 2402 of FIG. 35 isthat the CMD circuit 2404 of FIG. 35 is not included in FIG. 76B.

The commandable TAP architecture of devices 7102, 7202, 7402, 7502 and7602 can be substituted for any of the previously described commandableTAP architectures of the disclosure simply by providing the additionalCMD input signal 7104 and coupling it to the CMD circuit 2404 of CDR2402 in substitution of the TMS input, or coupling it to the CMD inputsof CDR 7204, CDR 7404, CDR 7504 or CDR 7604. A controller/tester coupledto the commandable TAP architecture of devices 7102, 7202, 7402, 7502and 7602 would provide the additional CMD input signal 7104 to CDR 2402.

While a single data register with a TDI input and TDO output is shown inthe devices of FIGS. 71A, 72A, 74A, 75A and 76A, parallel data registerswith multiple TDI inputs and TDO outputs, as shown in FIG. 69 , could beused in the devices as well.

Also while a single input (TDI) and single output (TDO) TCA is shown inthe devices of FIGS. 71A, 72A, 74A, 75A and 76A, multiple input andoutput TCAs, as shown in FIG. 70 , could be used in the devices as well.

Furthermore, while the CMD input is shown being a logic high input onthe CMD input signal 7104 of FIGS. 71B, 71C and 73 , it could be a logiclow input as well. Also, since the CMD input to the CDRs of FIGS. 71A,72A, 74A, 75A and 76A comes from the CMD input signal 7104, the TMSinput signal only inputs TMS data to the TSM 104.

FIG. 77 illustrates a controller coupled to a single device 7702, whichcould be device 7102, 7202, 7402, 7502 or 7602, via the device TAP's TDIsignal, TDO signal, TMS signal, TCK signal and CMD signal 7104. The TAPof device 7702 may operate conventionally in response to thecontroller's TCK and TMS signal inputs or in the commandable mode of thedisclosure in response to the controller's CMD signal input as describedin regard to FIGS. 71B, 71C and 73 .

FIG. 78 illustrates a controller coupled to a daisy-chain of devices7702 via a TDI signal to the first device, a TDO signal from the lastdevice, a TCK signal to all devices, a TMS signal to all devices, and aCMD signal to all devices. The TAPs of devices 7702 may operateconventionally in response to the controller's TCK and TMS signal inputsor in the commandable mode of the disclosure in response to thecontroller's CMD signal input as described in regard to FIGS. 71B, 71Cand 73 .

FIG. 78 illustrates a controller coupled to a daisy-chain of devicesconsisting of conventional TAP devices 7902 comprising TDI, TDO, TMS andTCK signals and commandable TAP devices 7702 of the disclosurecomprising TDI, TDO, TMS, TCK and CMD signals. The controller inputs aTDI signal to the first device, receives a TDO signal from the lastdevice, inputs TMS and TCK signals to all devices 7902 and 7702 andinputs a CMD signal to devices 7702. The TAP's of devices 7902 and 7702may operate conventionally in response to the controller's TCK and TMSsignal inputs. The TAP's of devices 7702 may operate in response to theController's CMD signal input from the controller as described in regardto FIGS. 71B, 71C and 73 .

Although the disclosure has been described in detail, it should beunderstood that various changes, substitutions and alterations may bemade without departing from the spirit and scope of the disclosure asdefined by the appended claims.

SOME ASPECTS OF THE DISCLOSURE:

Aspect 1. A process of operating a test access port within a device in acommandable mode to perform uninterrupted update, capture and shiftoperations to a target circuit within the device comprising the stepsof:

loading an instruction into the instruction register of the test accessport to select the target circuit and to enable the commandable mode ofoperating the target circuit,

transitioning the Tap state machine of the test access port to theShift-DR state to shift data to and from the target circuit,

inputting a command to the test access port via the test access port'sTMS input signal and while the Tap state machine is in the Shift-DRstate to cause the target circuit to cease shifting data, perform anupdate operation followed by a capture operation, then resume shiftingdata, and;

repeating the inputting of a command to the test access port to performadditional uninterrupted update, capture and shift operations to thetarget circuit.

Aspect 2. A process of operating a test access port within a device in acommandable mode to perform uninterrupted capture and shift operationsto a target circuit within the device comprising the steps of:

loading an instruction into the instruction register of the test accessport to select the target circuit and to enable the commandable mode ofoperating the target circuit,

transitioning the Tap state machine of the test access port to theShift-DR state to shift data to and from the target circuit,

inputting a command to the test access port via the test access port'sTMS input signal and while the Tap state machine is in the Shift-DRstate to cause the target circuit to cease shifting data, perform acapture operation then resume shifting data, and;

repeating the inputting of a command to the test access port to performadditional uninterrupted capture and shift operations to the targetcircuit.

Aspect 3. A process of operating test access ports within daisy chaineddevices in a commandable mode to perform uninterrupted update, captureand shift operations to boundary scan registers within the devicescomprising the steps of:

loading instructions into the instruction register of the device's testaccess port to select the device's boundary scan register and to enablethe commandable mode of operating the boundary scan registers,

transitioning the Tap state machine of the device's test access port tothe Shift-DR state to shift data through the daisy chained boundary scanregisters,

inputting a command to the device's test access port via the test accessport's TMS input signal and while the Tap state machine is in theShift-DR state to cause the boundary scan registers to cease shiftingdata, perform an update operation followed by a capture operation, thenresume shifting data, and;

repeating the inputting of a command to the device's test access port toperform additional uninterrupted update, capture and shift operation tothe boundary scan registers.

Aspect 4. A process of operating a test access port of a target devicein a daisy chained arrangement of other devices also including testaccess ports in a commandable mode to perform uninterrupted update,capture and shift operations to a selected circuit within the targetdevice comprising the steps of:

loading an instruction into the instruction register of the targetdevice's test access port to select the circuit and to enable thecommandable mode of operating the circuit,

loading instructions into the instruction registers of the otherdevice's test access ports to select a data register through which datamay be shifted,

transitioning the Tap state machines of the daisy chained device's testaccess ports to the Shift-DR state to shift data through the selectedcircuit of the target device and through the selected data registers ofthe other devices in the daisy chain arrangement,

inputting a command to the daisy chained device's test access ports viathe test access port's TMS input signal and while the device Tap statemachines are in the Shift-DR state to cause the selected circuit of thetarget device to cease shifting data, perform an update operationfollowed by a capture operation, then resume shifting data, and;

repeating the inputting of a command to the daisy chained device's toperform additional uninterrupted update, capture and shift operation tothe selected circuit of the target device.

Aspect 5. A process of operating a test access port of a target devicein a daisy chained arrangement of other devices also including testaccess ports in a commandable mode to perform uninterrupted capture andshift operations to a selected circuit within the target devicecomprising the steps of:

loading an instruction into the instruction register of the targetdevice's test access port to select the circuit and to enable thecommandable mode of operating the circuit,

loading instructions into the instruction registers of the otherdevice's test access ports to select a data register through which datamay be shifted,

transitioning the Tap state machines of the daisy chained device's testaccess ports to the Shift-DR state to shift data through the selectedcircuit of the target device and through the selected data registers ofthe other devices in the daisy chain arrangement,

inputting a command to the daisy chained device's test access ports viathe test access port's TMS input signal and while the device Tap statemachines are in the Shift-DR state to cause the selected circuit of thetarget device to cease shifting data, perform a capture operation, thenresume shifting data, and;

repeating the inputting of a command to the daisy chained device's toperform additional uninterrupted capture and shift operation to theselected circuit of the target device.

Aspect 6. A process of operating a test access port within a device in acommandable mode to perform uninterrupted back to back capture and shiftoperations to a target circuit within the device comprising the stepsof:

loading an instruction into the instruction register of the test accessport to select the target circuit and to enable the commandable mode ofoperating the target circuit,

transitioning the Tap state machine of the test access port to theShift-DR state to shift data to and from the target circuit,

inputting a command to the test access port via the test access port'sTMS input signal and while the Tap state machine is in the Shift-DRstate to cause the target circuit to cease shifting data, perform afirst capture operation, perform a second capture operation, the resumeshifting data, and;

repeating the inputting of a command to the test access port to performadditional uninterrupted back to back capture and shift operations tothe target circuit.

Aspect 7. A process of operating a test access port within a device in acommandable mode to perform uninterrupted update, capture and shiftoperations to a target circuit within the device comprising the stepsof:

loading an instruction into the instruction register of the test accessport to select the target circuit and to enable the commandable mode ofoperating the target circuit,

transitioning the Tap state machine of the test access port to theShift-DR state to shift data to and from the target circuit,

inputting a command to the test access port via a CMD input signal tothe device and while the Tap state machine is in the Shift-DR state tocause the target circuit to cease shifting data, perform an updateoperation followed by a capture operation, then resume shifting data,and;

repeating the inputting of a command to the test access port via the CMDinput signal to perform additional uninterrupted update, capture andshift operations to the target circuit.

Aspect 8. A process of operating a test access port within a device in acommandable mode to perform uninterrupted capture and shift operationsto a target circuit within the device comprising the steps of:

loading an instruction into the instruction register of the test accessport to select the target circuit and to enable the commandable mode ofoperating the target circuit,

transitioning the Tap state machine of the test access port to theShift-DR state to shift data to and from the target circuit,

inputting a command to the test access port via a command input signalto the device and while the Tap state machine is in the Shift-DR stateto cause the target circuit to cease shifting data, perform a captureoperation then resume shifting data, and;

repeating the inputting of a command to the test access port via the CMDinput signal to perform additional uninterrupted capture and shiftoperations to the target circuit.

What is claimed is:
 1. An integrated circuit comprising: a test data in(TDI) input, a test data out (TDO) output, a test clock in (TCK) input,a test mode select (TMS) input, and a command input; a data registercoupled to the TDI input, the TCK input, and the TDO output, the dataregister including: a data register capture input; and a data registershift input; a router coupled to the command input, the routerincluding: a router enable input; a router capture input; a router shiftinput; a router capture output coupled to the data register captureinput; and a router shift output coupled to the data register shiftinput; a state machine coupled to the TMS input and the TCK input, thestate machine including: a state machine shift output coupled to therouter shift input; and a state machine capture output coupled to therouter capture input; and an instruction register including: an enableoutput coupled to the router enable input.
 2. The integrated circuit ofclaim 1, wherein: the TDI input is a serial input; and the TDO output isa serial output.
 3. The integrated circuit of claim 1, wherein: therouter includes: a first multiplexer including a first multiplexer firstinput coupled to the command input, a first multiplexer second inputcoupled to the router capture input, and a first multiplexer output; asecond multiplexer including a second multiplexer first inverted inputcoupled to the command input, a second multiplexer second input coupledto the router shift input, and a second multiplexer output; a firstgating circuit including a first gating circuit first input coupled tothe first multiplexer output, a first gating circuit second inputcoupled to the router enable input, and a first gating circuit outputcoupled to the router capture output; and a second gating circuitincluding a second gating circuit first input coupled to the secondmultiplexer output, a second gating circuit second input coupled to therouter enable input, and a second gating circuit output coupled to therouter shift output.
 4. The integrated circuit of claim 3, wherein: thefirst multiplexer is coupled to the second multiplexer.
 5. Theintegrated circuit of claim 1, wherein: the data register includes aplurality of serially coupled scan cells coupled to the TDI input andthe TDO output; and each of the plurality of serially coupled scan cellsincludes a data input and a data output.
 6. The integrated circuit ofclaim 5, wherein: each of the plurality of serially coupled scan cellsis coupled to the TCK input.
 7. The integrated circuit of claim 5,wherein: the data register includes a clock multiplexer coupled to theTCK input and to each of the plurality of serially coupled scan cells.8. The integrated circuit of claim 1, wherein: the data register is atest compression architecture.
 9. The integrated circuit of claim 8,wherein: the test compression architecture includes a demultiplexercoupled to the TDI input and the TCK input.
 10. The integrated circuitof claim 9, wherein: the test compression architecture includes amultiplexer coupled to the TDO output and the TCK input.
 11. Theintegrated circuit of claim 10, wherein: the test compressionarchitecture includes a plurality of parallel scan paths between thedemultiplexer and the multiplexer.
 12. The integrated circuit of claim11, wherein: the router capture output and the router shift output arecoupled to the demultiplexer, the plurality of parallel scan paths, andthe multiplexer.